Whenever I am designing patterns for products, I make a seamless 64x64 cm pattern using Illustrator. When I make these patterns, the transform, align, and pathfinder tools are the handiest for this. I, then, design the product, and create each section where the stitching would be located. I take the seamless pattern and apply it to each panel. I change the orientation of the seamless pattern on each panel because more than likely, the factory won't line up the patterns exactly. I also include the measurements of at least design element so the factory would have a reference on how big the seamless pattern should look like on the product.