I had looked online for a platform bed for my queen-sized memory foam mattress. All I could find were pricey ones or boring one on the lower price end. I saw that cubical shelving was on sale at my local home store, so I decided to design one myself out of the shelving. I wanted a bed with storage, so here is what I came up with:
It is all very simple really. I bought 4 sets of the 6 cube shelves.  These were the base of the bed. I just put them together according to manufacture instructions. The just lay flat on the floor, not set up like shelves and makes for a pretty sturdy platform:  http://menards.com/main/tools-hardware/shelving-storage/decorative-shelving/6-cube-cubber-cherry/p-1723202-c-12169.htm Then rest of the shelves that wrap around the platform part are the 9 cube shelf sets.    I have 4 sets of these too and they just stand along the wall and the base is just bumped up against them. (This pic only shows 3, but I added another one to the right side of the pic.) http://menards.com/main/tools-hardware/shelving-storage/decorative-shelving/9-cube-cubby-cherry/p-1469355-c-12169.htm  I left them free standing and didn't attach the sets together, because I wanted to be able to move it easily in the future if I need too. But I am sure that it could be done to make the headboard more stable.
For the platform that goes on the base, I had 2 pieces of fiber board cut at the lumber yard to fit my mattress. My mattress is a short queen. I little shorter than a standard queen cuz it was the one we had in our camper. To make the fiberboard look better and be softer, I used a staple gun to attach a set of inexpensive brown sheets to cover the boards. I used the top sheet for one board and the fitted for the other. I just stretched it over the boards and stapled it to the bottom. The reason I used 2 boards is because they don't sell the boards as big as I needed to fit a queen bed, and also I wanted to have some storage under the boards in the cubbies and I can lift the end of the mattress to keep stuff in there. I found cube shaped boxes after Christmas on clearance that fit perfectly into the cubbies.
 
That is basically all there is to it. I just have a memory foam mattress that sits directly on it. I don't have a box spring, so if use a box spring, the mattress would sit up higher than mine does.