The corners - point F - run in a smooth arc from the vertical edge at K to a distance of about 5 inches / 12 cms further out from where the vertical edge of the cloth would be. The sharper this point is, the easier it is to tie the ends of the braies up to a braid.
ConstructionDepending on the width of the material, you may have to add, as I did, a short extension to the front of the fabric (this is the flap at the bottom of the diagram). After this is done, construction can properly start.
Fold down the top between A and B along the line at J and stitch to make a tube. Similarly, fold up and stitch the bottom extension along the line at I . These tubes will contain the drawstring.
As the pattern is symmetrical, only details for the left leg are given. Stitch point H to K , and stitch point I and J together. Join up the seam between these points.
The resulting gap B / J / I / E at the top of the braies' drawstring tubes can be left as a slit for the left hand hose tie, although I've stitched this gap together where it lies behind the drawstring next to the body, to leave only the front of the slit open.
Once both sides have been done, at this stage the basic gusset / braies shape is formed, and it is only necessary to finish off the legs. Again, only left leg details are given. With the leg G / H / K / F taking shape, stitch down from the join at H/K for about four inches / ten centimetres, to leave a long slit up the inner leg. Finally, complete the right leg and hem all the edges.