Arrange three of the 6-foot 2-by-10s parallel to one another, standing on edge on top of the plank -- on a 6-foot by 2-inch side -- 20 inches apart.
Cover the three 6-foot 2-by-10s with the 4-by-6 board, screwing the board into the beams. Use at least eight screws for each beam. Arrange one of the beams along a 6-foot edge, one about in the middle and one four inches from the other 6-foot edge.
Flip the board and beams over and attach the other board to the other edges of the beams, aligned with the first board.
Arrange the other beams on the ground, parallel to each other, 2 feet apart, in ascending order: first the 2-by-2, then the 2-by-4, the 2-by-6, the 2-by-8 and the 2-by-10.
Lay a 6-by-10 board over them -- it will be slanted -- with the 2-by-10 directly beneath one 6-foot edge. The other edge will touch the ground 2 feet beyond the 2-by-2. Attach the board to all of the beams with 2-inch screws, using at least eight screws on each beam.
Flip the board and beams over and attach the other 6-by-10 board to the beams.
Slide the wedge -- made with the 6-by-10 boards -- beneath the overhanging edge of the rectangular platform that was made with the 6-by-4 boards. Mark the spot of the rubber, in the center of the 6-foot crease between the parts, six inches onto the platform. You can mark the spot or paint a rectangle to mark the location of the rubber.
Surface the wood with polyurethane or artificial turf for an extra touch.