The trend over the last few years has been to paint canvases with the staples on the back. This allows the sides to be painted. Canvas can be hung without a frame, which reduces cost. A number of Art shows now require these types of canvases that eliminates frames for a unified showing.
The challenge with these canvases is that the holders for studio easels clamps to the top and bottom sides, making it next to impossible to paint. Usually I’d wait for the paint to dry and then paint the missed areas which could result in colors that don’t match up.
One solution was to tape the canvas to the back of a board and place that board on the easel. This worked OK for a short stint, but if I painted on the canvas for several days the tape would usually give out and the canvas ends up laying, wet side down, on the floor.
The solution for me was to take some scrap plywood and cut it to length to fit my easel.
A line of screws was placed toward the top of the board for the canvas to hang from.
The canvas is then prepared by installing a wire hanger and some tape to keep it from moving while being painted.
Secure the holder in place on the easel. Now hang the canvas on the screws using the wire. Using all the screws increases stability of the canvas while you paint it.
Below are two of my studio easels with the plywood setup. This has worked very well for me. I can now paint all of the edges in real time and I no longer have canvases falling on the floor.