Arrange four 3-inch-wide, 3-foot long wooden planks into a square on the ground, then staple the corners where the planks touch using a staple gun and 1-inch-long staples.
Repeat this process to create a second wooden plank square.
Place another 3-inch-wide, 3-foot-long wooden plank standing up vertically at one of the corners of one of the plank squares. Staple the plank in place.
Repeat to staple vertical planks at each corner of the square.
Place the other wooden plank square on top of the form, allowing the tips of the vertical planks to overlap the corners. Staple the corners in place.
Insert a leaf bag down into the center of the leaf bag holder, then fold the edges of the leaf bag over the top of the holder.