I hope I understand your question. Let me tell you how I put together a bag. I quilt a top layer, batting (thin) and muslim together for the outside of the bag . I sew the front of the outside bag to the back of the outside bag pieces. I use iron on fleece and iron it to the lining. I then sew the lining front and back together leaving a 6" or so opening on the bottom. Then when ready (after straps have been added), I sew the "outside bag" and the "inside lining" together at the top. Then you turn the bag inside out. Press the top and then sew 1/4" from the top edge (top stitch).
An excellent pattern to learn how bags are put together is a pattern for the Bow Tuck Bag. Her instructions are excellent.
For application of zippers ----- someone has a tutorial here that would help with that.
good luck