Generally speaking, I use commercial floater frames, and I prefer the Illusions frames from Jerry's Artarama. However, I have a number of canvases I have in dimensions that are not available.
I therefore decided to try a simple test using a really simple approach, simpler than the ones that I had seen. The designs I had seen seemed to be beyond my sketchy carpentry skills.
As a test I selected a small 16" X 20" gallery wrap canvas with 3/4" depth. You can get this size, but it seemed like something that would be easier for an experiment.
To make the frame, I chose a length of inexpensive 1" X 1" milled angle and an inexpensive 1" X 1/4" thick strip. Gluing the two together makes a frame that is 1" deep on the outside and 3/4"depth on the inside.
Now normally you have to use more pieces, but I realized that if the inside of the frame was a little large--and here is the tricky part--the painting were fastened to the back lined up just right, you could make a floater frame with just two parts. There's a trick, using tape.
Now some people might choose to cut first and paint the black last, or paint the black first, it's up to you. I'd advise using the method you think you are the least likely to mess up.
I put painters tape on the top edge and then did a coat using Liquitex clear gesso right up to the edge. I then did a second coat mixing acrylic black into the clear gesso and painted almost up to the edge, and then finished the edge with a small brush.
Since I am leaving the wood frame unfinished, I can sand away any mess ups, as long as they are not too bad. This produced excellent results as the black was very matte and totally nonreflective. It looks like a hole, which is what you want. You could also use black gesso, or a very flat black paint. (Don't use gloss.)
I combined pairs of those little wood wedges that you get with prestretched canvases glued together as guides. Using a hand saw with a fine tooth and a mitre box, I cut out the four sides, using the width of the guide for the extra amount of space to leave around the painting. (Note if you are bad at math, the frame must be the dimension of the painting plus twice the size of the guide.
I used a clamp to glue and join two sides at a time.
I then placed the painting face up inside the frame, and placed guides around the painting to make sure it is correctly centered. I then fastened it in temporarily into position with non-stick painter's tape. I then removed the guides.
Please note it is your responsibility to make sure your painting is dry and will not stick to the tape when you remove it. (This is a dry acrylic painting protected with a couple of layers of Soluvar varnish.)
The painting, "Oceana Pacifica", face up secured with tape. Don't try to skimp on tape, especially if you are securing a large piece!
Properly positioning the piece and making it secure is the secret to not having to do fancier carpentry.
Here you see the piece flipped over on a soft approximately clean carpet.
In the background, you can see the corner of a commercially prepared floater frame.
Screw in, preferably using dogleg brackets. (These are hard to come by, but there were some extras in the frame kits I have bought.) Add a wire to hang it. Remove the tape.
(Did you put the wire on the correct (top) side? Good.)
The finished piece.