Okay... then I'd start with the contrast fabric on the table wrong side up, then put the batting on top and then the fabric that will be the outside of the bag on top of those with the right side up. You can quilt using masking tape if it's just a diamond design. If you haven't quilted before you probably don't have a walking foot so the fabric may bunch a bit as it sews. Can you scan the directions or something so we get a better picture of what they want?