Since these breeches do not have fall extensions, turning the edges of the cuts is not an option. Make sure the fall cuts are parallel to the center front seam and slightly shorter than the height of the bearer. The fall is around eight and a half inches wide. The cut should overlap the bearer about 1/4" at side and bottom as shown here. The fall is tucked under for clarity.
Make sure the top edges of the bearer and breeches line up, and back stitch along where the pins are in the photo. Overcast the edge of the bearer to the inside of the body if desired. The lining is going to overlap, so it isn't really needed.
To protect the edge of the fall, a separate fall yoke is added. This T-shaped lining piece has it's top and side edges turned and it is back stitched right to the edge of the fall. After that is in place, the fall can be pinned closed. A short (1/2") horizontal back stitch right at the base of the cut secures the fall to the bearer underneath and prevents tearing.