The kirtle is the outer-most layer of clothing for a peasant woman on the manor. The costume notes go on at some length about various styles of gowns: ignore them. You don't need one of these unless you're gentry, a housekeeper, or are in another status role; just stick with the kirtle and you'll be fine.
The kirtle is in effect the dress bit of the outfit. Pictures of my first kirtle can be seen in the guide to clothing layers and my latest one is photographed in gratuitous detail and displayed in the gallery. This guide, by the way, was lifted in great part from the explanatory notes in the yellow kirtle diary. I'd strongly recommend reading the two together to get an idea of how this actually works in practice.
Basically, other than colour, these garments are pretty similar. They consist of a tight-fitting, front-lacing bodice and a lined, pleated skirt. Although I'll be describing - and very largely sewing - these two components seperately, remember that they're joined together to make a single garment. Turn up at costume check with a seperate bodice and skirt and odds are you'll be given needle and thread and asked to join them together.
Kirtles can be either made sleeveless - as both of these are - or with sleeves attatched. I'd strongly recommend the former. It's easier to make (putting on sleeves is a pain) and on hot days on the manor you'll be glad you can take your sleeves off. For cold days, make up a seperate pair of sleeves that can be laced onto the kirtle. Instructions for these are here.
What you'll need
As with any garment, the first thing you need is a pattern. The pattern for the skirt is dead easy and I'll be talking you through that when we get there. The bodice is more tricky and to an extent you're on your own here. My pattern, made as it was by trial, error, and creative disaster management, won't work for anyone that isn't precisely the same shape as me.The best advice I can give is to look at lots of portraits to get an idea of the size, shape and fit of garment you're aiming for. It's a very different feel from anything you're likely to have worn in the twentieth century. The major difference is how much snugger it is: the bodice should be tightly fitting when laced, in order to support the breasts (and it's best to make it a couple of inches too tight to fully lace closed, because it will stretch on the manor). It finishes at the natural waist, which is the point you bend from, and is typically above the point that jeans fit to. If it's any longer it will collapse into horrible wrinkles across the back on wearing. The waistline can either continue horizontally at the front or, for later years, can drop into a slight point. The latter is probably more flattering for a modern eye, but is slightly more tricky to sew. Your call.
The position of the top of the bodice is relatively critical: too low and the breasts will spill over and be uncomfortable; too high and they'll be flattened not uplifted. I tend to lift mine as high as they'll go and work to the top of the nipple. There's some evidence for the underbust look in the latter half of the sixteenth century but ideas of what it's acceptable to wave around in public have changed, and I wouldn't recommend it for the manor!
There are a few resources online that may help in drafting a pattern. There's a pattern generator here which should get you in the right ballpark and this kirtle pattern is also useful. If you're using the latter remember Kentwell peasant bodices are almost always front lacing so you'll need to adapt your pattern to allow for that.
Alternatively, you can always go for the tried and tested method of a friend, a pile of calico and a bottle of wine, and try draping a pattern. Again, adapt it to be front opening, and reduce the point at the bottom of the bodice. However you go about it, it should end up looking something like this...
That's my pattern to the left. It's made up of two pieces - a large front piece and a very small back piece. The shoulder strap comes up from the back, and will run over the body and join onto the bodice front. This should be cut a couple of inches longer than you need it. This pattern is a little unusual, in that it produces three seam lines very close together on the back. The yellow kirtle diary discusses this in more detail, and explains why I do it that way.
In the second picture, I've drawn a line with photoshop to show where most women on the manor place their seam. Again, this is a two piece pattern - just pretend that the seam near the back isn't there. This pattern is undoubtedly easier to draft - the seam runs straight up and down at your side - so I'd recommend going with that.
The third picture shows another seam placement, which can be seen in some surviving portraits. I keep meaning to try this one. In all three of these, the centre back seam is optional - the two back pieces can be cut as one.
Finally, it's possible to cut the bodice in one piece, with no seams at all. The seams are all straight lines, so there's no reason why you can't just lay the pattern pieces together and cut the fabric out as one piece. This is undoubtedly the quickest construction, but there's less flexibility if you need to adjust the thing. It's also less efficient of fabric and, if you're using patterned fabric (which as a peasant, you shouldn't be) you'll lose control of which way the pattern runs.
Whatever method and pattern you go for, the first stage is to cut out the pattern pieces in calico, making sure to cut them too big. Tack them together, wrap them around yourself (a good friend helps for this) and eyeball them. Adjust the calico til it looks right, take the thing off and mark where your seams are. Dismantle it, cut along those seam lines, lay it out on card and make a copy. That should be dated and tucked away in a file somewhere: it's your master pattern and, now you have it, your next bodice can be made by making adjustments to it rather than by having to go through the whole palaver of starting from scratch. A little unusually, this pattern should not include seam allowance; the guide will explain why.Onto making the bodice.