Actually, you do mokume in a press fixture in an oven. Take sheet stock and sheet solder and build a stack of sheets and solder chips placed in a pattern between the layers. Clamp between two plates of steel and heat until you exceed the flow temp for the solder. Bake for an hour, allow to cool... mokume block. You may now hammer patterns into this block or work it with cutter tools to shape. It's essentially an oven braze operation, keep everything CLEAN, there's no such thing as too much flux.