Cut the three legs from the 2 by 3 boards. Cut two legs 82-3/8 inch long and the third 81 inches long. Cut a 45 degree angle on the top of each board.
Measure 78 inches from the bottom on the two longer legs and drill a hole. Drill two holes on the third piece, at 39 inches and 74 inches from the bottom.
Lay all three boards on the floor with the shorter leg in the middle. Place a bolt through the upper hole on all three to attach loosely, and spread the legs so that the feet sit 45 inches apart before tightening and securing with nut.
Place the 4-foot board 38 inches from the bottom of the two longer legs and secure with bolts and nuts onto the two front legs, making sure the legs stay 45 inches apart.
Put an eye screw in the middle of the horizontal board, and in the back. Put a second eye screw at about the same height on the rear leg. Tie a piece of twine, or affix a light chain through the eye screws to keep the easel in position.