When I design from my head, from scratch, I create a problem to solve with a dimensional object and some set of materials. For example, a piece can have only one leg, or be made from existing structures, or contain hidden electrical wires. The problem is a limitation and a starting point. If the piece is furniture or in some way functional, then there are limitations to consider like human bodies and gravity. Will it be seen from above? Is it sharp? Can it get wet?