We all have ways of making our totes and making them comfortable for us. I am cutting my scraps at 29 inches but when I sew them to the front and back I place them 3/4 inch beyond the top edges. I do that so when I topstitch at finish I catch the ends again. I place my handles 7 inches apart or 3.5 in from centers. On this one I had used the 809 iron on pellon and pieced my front and back like you told me. However I quilted my lining to the foam. I didn’t use any binding but all my seams are edge finished and enclosed. I boxed my corners by cutting a 2 inch square out of each bottom.
After piecing my front and back I cut them 17 inch square. I quilted foam to front and back lining before citing to 17 in sq . I edge finished by serging all raw edges of all main F & B and lining F & B. I placed F & B right sides together of main tote and also lining. I sewed together at sides and bottom edges. I then cut 2 inch square out of corners of lining of Front & Back. To box corners I placed side seam and bottom seam evenly and stitched across. I edge finished all corners.
I had made my handles previously and now I sewed them to F & B as stated above, after turning F & B right side out. Then I just slipped F& B inside lining. Sewing all around the top edge except leaving an opening , about hands width, for turning right sides out. I pressed top edge, then sewed close to top edge all around, sewing opening closed. No need to bind anything although the binding does add color to top edge.
To piece the Fat Quarter front and back ‘correctly’ of the main outer body you better ask aashley, as you can see I made mistake with one side.