Harbor Freight 10 x 12 Greenhouse Base Modification. Setting up your greenhouse using 4x4 pressure treated lumber instead of the metal frame that you partially bury. I think this gives you a much sturdier base that almost eliminates needs for additional crossbracing that others have recommended. I get practically no flex in the structure with my base mod. I did seal the edges of the polycarbonate panels as well securing them with screws.