You can make your straps however you want but I like to make my straps then place them in between the exterior and lining and topstich the top, or i place them on the outsides and sew tyhem down. I think it depends on how you want your straps to look check uner the tutorials list and you will find many different ways. Good luck and post a pic when you are done.
i guess my situation is different I started crocheting at 16 on and off then I taught myself how to sew last year and because of sewing I started back crocheting . for me the sewing brought out the crochet in me