I made several such type quilts as consignment quilts. Look at the second picture is this link.
http://www.quiltingboard.com/picture...de-t52466.html
Yes, you cut the front of the quilt. Sew any seams shut that you want sewn shut. I left pockets etc. open. then I over sized cut the fronts, ironed light weight interfacing onto the back. I then took several such pieces and made a large block, I added anything else like socks or a hat at this point, and then squared up the block. At the end sewed all the blocks together and treated it like a regular top. Just be careful when ironing on the interfacing as many of the decals and screen prints will come off and can't handle being ironed. Also be careful with quilting due to thickness and the many buttons, zippers etc. I normally cut the zipper out before I would sew a jacket or such shut. i would also cut away any bulk I could. These quilts can get too heavy really fast.