When assembling furniture or other larger projects, some pros don't use either the tops of their workbenches or the floor. Instead, they use two or more wooden boxes about 18 in. high, 24 in. wide and 32 in. long, set upside-down on the floor to span the project's length. The project boxes don't need to be fancy, just provide enough height to cut down on back strain. The boxes can also be stacked, or set on their sides or ends, to provide for varying heights.
Make sure to always install a drip cap flashing over the head casing of all doors and windows. A flashing will prevent water from penetrating the door or window frame.