Measure the length and width of the oil painting. Purchase a wooden picture frame that is 2 inches deep with the same length and width measurements.
Take the backing off the wooden picture frame and discard it.
Place the frame onto a flat surface with the bottom side facing upward.
Put the oil painting into the frame. Allow the canvas frame to sit against the frame bumpers inside the casing.
Hammer 8 to 12 small 1/2-inch-long nails around the inside edge. Angle the nails at 45 degrees so the end of each nail prevents the canvas from moving. Space the nails out evenly around the inside perimeter of the frame.
Hang the picture frame onto the wall.