This is a very easy project if you have a sewing machine and basic sewing skills.
One pair of jeans that fit you well before you were pregnant
One t-shirt that fit you very snugly before you were pregnant (maybe even a size too small)
Scissors, seam ripper, pins
Sewing machine, coordinating-colored thread
Piece of soft elastic long enough to go around your hips or above your belly
Step 1: Start with jeans and a t-shirt.
The jeans should have fit you well before you were pregnant, and the t-shirt should be very snug.