Do you love the look of a boy short with the scalloped edge of the lace at the leg instead of elastic? Stretch laces with spandex in them are exactly what you need to make that happen. Here's how to alter the pattern.
Gather together your boy short pattern (you can learn to draft them to your own body measurements from the Make & Fit Panties book) or use any commercial boy short pattern. You will need to make the following changes to the pattern. Remove the elastic allowance from the bottom hemline (if there is one).
A boy short almost always is a one-piece pattern, but to make a lace edge leg, we need it in two pieces. Decide where you would like to divide the front into panels. It can be virtually anywhere on the front half of the panty (more toward B than A). Draw a line parallel to the centre front seam to the hemline. Connect the bottom of the side seam to the inseam edges as shown.
Separate the two pieces and label them A (back) and B (front)
Use the chosen lace as a measuring tool. Align the deepest part of the scallop of the lace (called the LoPoL) along the bottom hem line. If the lace is wide enough to fit pieces A and B, add the seam allowance to the edges between A and B, and you are done.
However, and this happens more often - if the lace is not as wide as piece B, you will need to have the laces in the back overlap. To do this, draw a seamline about 1/2” (12 mm) below and parallel to the Low Point of the Lace (LoPoL).
Separate the three pieces and add seam allowance of 1/4” (6 mm) between A and B. Allow a 1/4" (6 mm) allowance along the bottom of C, as we will be overlapping the lace edging of C onto the lace edge of A.
Cut out the three pieces A, B and C from the lace edging, making sure to mirror the lace by cutting the left side of A,B and C from one edge of the lace and the right side of A, B and C from the opposite side of the lace. If the lace motifs match exactly when the right sides of the lace are put together, you know you have done it correctly.