To make a pattern, fold your crop top in half and trace around the edges adding a half inch seam allowance. If you want to skip this step, just lay the shirt on your fabric and trace around the edges, also leaving a seam allowance. Depending on your fabric, you may want to double up and cut two pieces each for the front and the back. For mine, I only lined the front piece.
Place this piece right sides together with the other front piece and sew around all the edges except for the bottom. Turn it right side out and top stitch the neck and armholes.