I've used drop-ceiling tiles as a building board many times.

The door's a great idea if you have the space, if not drop ceiling tiles make for a suitable board. They are also "flexible" enough, that if you find one to be a little warped, you can turn the concave side down....and it will flatten itself out on the table or counter top or whatever you're using.

Just remember....before you even open the box....make sure whatever you're building on is flat! Your airplane will only be as straight as your building surface.

EDIT: It's also nice to have like a 48" ruler handy, a torpedo level, and a builders' square...or whatever they call those 6" triangles with a 90 degree side