Here is a unpattern I designed for a big, roomy peasant-blouse-type top. It fits my 48″ chest with loads of ease; I wear it with corsets so it works as a liner too. It is not too long so it doesn’t poke out of the bottom of the corset. I make it out of muslin or voile.
The pieces are basically rectangles with two corners cut off;
Here are cutting layouts for the two standard fabric widths.
So you will need about 1.8 yards of 44″ wide fabric or 1.1 of 58″ wide. Although the layouts don’t really show this, the pieces will be very nearly up to the edges of the fabric, so if you’re going to dye your fabric, do that first as the edges of some fabrics dye darker than the rest (due to the weave being a little tighter).
You will also need 40-50″ of elastic for the neck and 2 x 12″ for the sleeves.
Here are the pieces cut out:
To sew, first French-seam the diagonal seams (shoulders) like so:
I’ve put rulers along the seams to show where they are as unsurprisingly, white stitching doesn’t show on white fabric.
Then, fold in half so the front and back are together and French-seam the underarms and sides.
Hem the bottom.
Hem the neck and sleeves, leaving the hem deep enough to thread elastic through (and a gap to do so). Thread the elastic through and safety-pin the ends together; try on to make sure the neckline fits how you want and sew the elastic ends together, and sew up the elastic openings.
You can also make a smaller version if you want less ‘puff’, are smaller in the chest, or have less fabric to work with. For example I have made one with sleeves 14″ deep and 20″ wide, and the front/back 20″ deep and 29″ wide. I didn’t add elastic to the sleeves for this one.