I had more fun building this floater frame a few months ago to replace a painting we had over the fireplace. The older painting was a gallery wrapped painting and I had just finished this new piece on standard stretched canvas which is 5/8" thick stretcher bars I think. I picked up a piece of oak at out local lumber yard that was slightly over 6" wide. I wanted to make this floater frame with 3" deep sides so this would work.
I cut all of the side pieces on my table saw and began piecing it all together. I won't post any dimensions because these frames I make are always different dimensions depending on the size of the painting.
After all of the sides and back pieces were cut I glued and shots brads into the corners to keep it all together. What you see here are the side pieces and two strips placed inside to attach the painting to. Long wood screws go through these wood pieces and into the back of the paintings stretcher bars...that is how it mounts.
To reinforce the frame I add strips of wood along the back making the frame basically an "L" shape.
Here is a closer view of the corner before the back piece is added. You can see the small brads shot into the corners. These are later covered with wood putty so you don't see them.
Here is a view of the back pieces now mounted to the sides. Any gaps in the wood are filled with wood putty and then sanded.
....and here is that same area after sanding, staining and rubbed with wax....looks cool!
After the frame is all glued, nailed together, sanded and stained it is then rubbed with furniture wax to protect the wood and give it a nice luster.
Once that was all done I mounted the painting. It is centered and then the screws go into the back wood pieces and into the paintings stretcher bars. Since you have to work in the back putting in the screws it is easiest to do all of the mounting standing the frame upright. I use the little corner tensioners that come with stretched canvases to level the painting and then just do all of the drilling from the back
Below are a couple of detail shots of how the painting stretcher bars mount to the center mounting bars. Basically, you predrill holes into the mounting bars. Then you screw through the mounting bars directly into the back of the paintings' stretcher bars. If you look at the photo above you see I used corner wedges stacked up the the height I wanted the painting mounted to the frame. Then all I had to do was move it evenly from side to side and then drill screws into the back to attach the painting to the mounting bars. My stretcher bars are 5/8" thick, the mounting bars are 3/4" thick...both of these fit well into the 3" deep frame.
...a little closer view of the mounting bar and stretcher bar area.....
And then it is all done and ready to hang......
To get an idea of the size of this frame that is a french easel it is leaning against...big frame! Doesn't weight that much because the wood is only about 3/8" thick. To keep the wood from bowing is one of the reasons the back pieces are attached to it...they stiffen the frame.