Braies

Simply put, braies are medieval boxer shorts. Braies would have been constructed from linen and typically would have been undyed or bleached white. Combined with a linen shirt, braies would have comprised a linen base layer that would have been more comfortable to wear against the skin than wool and which would have been more easily washed. Neither of these garments were found intact on the Bocksten man, however linen tends to be more susceptible to rotting than wool or leather, and so it is reasonably likely that these garments rotted away. It is also possible that the Bocksten man was not wearing a linen underlayer, however there is plenty of evidence from other sources to indicate that such garments existed and were worn.

Farm workers wearing only their braies. Image from the Maciejowski Bible, a 13th century manuscript.

Wool or linen chausses would have been used to cover the foot and lower leg and would have been pulled over top of the bottom edge of braies such that the entire leg was covered. These chausses would have been tied to a belt at the waist that may or may not have been part of the braies.

Braies and Chausses tied at the waist band.

There is some debate concerning the appropriate method of constructing braies and over whether they were a pair of sewn "pants" or whether they were actually accomplished by simply cloth wrappings, similar to the undergarments worn by ancient Romans. Accomplishing such cloth wrapped braies is rather simple, as it involves the creation of a single rectangle of fabric approximately 60" x 40"-50" which is conveniently about 1.5 yards of linen fabric. This cloth rectangle is then wrapped around the body and rolled over a belt. The link below provides a picture tutorial along with instructions (that appear in Swedish and English). Getting the exact measurements probably takes a little playing with the wrapping process and a little practice, but once you've figured it out, making this style of braies is as simple as cutting the fabric to size and finishing any raw edges by rolling the fabric over twice and stitching into place.

Cloth Wrap Braies

Braies can also be sewn together to form a pair of short pants as we might think of them modernly. This site: sewn braies provides images of several types of braies along with the patterns for making them. Their recommended pattern shown below is essentially a rectangle for each leg and a square gusset in the crotch. You might slightly improve this pattern by adding about two inches in length to each of the leg pieces and then rolling the waist band back over itself to form a channel for a waist band.