I've been keeping bees for 6 years now. I have always Built My Own boxes, bottom boards, inner covers and outer covers it is easier to just buy the frames. You don't have to be experienced beekeeper to build your own boxes you just got to know how to read a measuring tape. I just finished a run of seven six deep boxes and one medium I always use wood that I find in dumpsters shelving boards and 1x12 tongue and groove work really good I'll include some pictures one of them is the instructions that I go off of.
