So I finally got around to getting the instructions for my DIY sofa from my boyfriend and he took a few photos to illustrate some key points. Sorry for the delay folks but I have a terrible memory and have been super busy lately. These are in his words, including the title (which I don't want to take credit for LOL). (Thanks Jeff!!)
First thing is to measure the cushions you are going to use (we used the Ikea's Lillberg sofabed cushions). You want the cushions to fit tightly into the sofa. This will keep the cushions fluffy and in place as you get comfy. The pillows should sit 2-3” below your sides depending on the height of your pillows. You can see the difference in this picture:
The frame is made from 2x4's, the width ones that attach to the legs are first and then 2x4 lengths lay on top around the edges.
Another 2x4 is cut to fill in the gap so the 2x6’s on top sit evenly.
FYI – do not screw your wheels/legs to the couch like this. Use proper screws, something I forgot on the trip to Home Depot. And we're going to switch out 2 of the casters on each of the 2 moveable pieces to finials, because despite using lockable casters, they still move around too much.
Lay some 2x6’s lengthwise on top. You could use whatever width of wood you want, heavy is good so the couch won’t move around when you are. You can see in the first photo an end view without the MDF.
The ledge on the back was made by raising a 2x6 so it would make a space for pillows. If you are going to make a pillow ledge remember to take that into account when making the frame (it was an afterthought on this one).
The sides are finished with the MDF and cut at 45 degree angle at the corners.
The MDF we used (8") is the perfect height to reach from the top of the legs to 2-3” above the frame. The couch sits 12” high to the top of the MDF.
Fill the holes and cracks, prime (we bought pre-primed MDF), paint and accessorize as required (mine still require new pillows - hoping to tackle that ASAP).