I never recommend any kind of commercial products. But I have to make an exception of this one kind of frame. As far as I can see it is the only thing to use on my paintings, if you can find one to fit.
Take it to a framer and have them glue it onto a ½ inch or thinker foam board. Hard foam will not warp. Of course you can do this yourself and save a lot of money. Then put the mounted canvas into one of these frames.
Don’t let the framer stretch the canvas! I had some dolt do that and he put staples all around the edges of the canvas, despite that I told him not to. The canvas was ruined. Then I had to pay him to put a frame on it just to hide the staples. But the canvas was still ruined; it could never be stretched!!!
Unfortunately I used to paint 8 x 11” pictures and some other odd sizes that there are no ready made frames to fit.
From now on I will paint only 8” x 10” and 16” x 20” ….except for possibly a few 4 x 5” canvas boards that do not need to be framed.
House foam insulation comes in one inch thick and will fit in some frames like this one. dickblick.com/nielsen-metal-frame-sections-matte-black-style-22/