You can set up a semipermanent workstation with sawhorses when you’re working outside. Screw 2x4s to the tops of the sawhorses and a plywood platform to the 2x4s and you’re ready to build. Let the 2x4s project a few inches beyond the plywood to make it easier for someone to help you pick up the whole works and move it around as needed. To keep the clutter out from underfoot, install a temporary plywood shelf across the braces.