3 ideas
Any bag can be decomposed into a fixed vocabulary of components — body, gusset, base, flap, strap, handle, closure, and hardware — each serving a distinct structural or functional role. Designing systematically means specifying each component independently, so changes to one (e.g., gusset width) can be reasoned about without rebuilding the whole.
A material's drape, thickness, and rigidity — its 'hand' — dictates which construction techniques are viable, not the other way around. Stiff leather demands turned or bound edges and structured seams, while soft textiles require lining, interfacing, or piping to hold shape, so material selection silently constrains the entire build sequence.
Zippers, clasps, rings, and rivets are the locations where a bag actually fails under stress, so they should be specified by load and friction tolerance rather than by appearance alone. Viewing hardware as engineering joints rather than decoration reveals why stitch reinforcement and attachment method matter more than the visible finish.