Lay 33cm length of lining material on a flat surface and make a small mark along its length (16.5cm). Make a mark halfway along the length of the lining fabric (22cm x 12cm) and lay it on top of the interfacing material. Lay your outer purse material (22cm x 12cm) on top of the interfacing material right side up.
Fold the outer edges of the lining material over to meet the outer fabric and press them flat with an iron. Fold them over again so the fold is at the point where the lining material meets the outer material. Press the folds flat with an iron.
Stitch along the inside edge of each cuff, 0.2cm in from the fold. Fold it in half, so the two cuffs rest on top of each other and the purse is effectively inside out. Sew along one side of the purse, approximately 0.6cm in from the raw edge.
Sew up the other side of the purse, approximately 0.6cm from the raw edge. Cut away the excess material on either side of the purse (2-3mm from the seam) and zig-zag stitch along these raw edges to neaten them and prevent fraying. Tidy any loose threads.
Finally, turn the purse right side out and use the blunt end of a crochet hook, pencil or similar to push out the corners. Lovely little snap purse is ready!