Step 1: Base Layer
Take two ¾” x 4’ x 8’ sheets of OSB and set them down on the floor side-by-side. These sheets run lengthwise, i.e., “front-to-back” in terms of your platform’s orientation (Figure 1).
Note: These sheets are commonly referred to as ¾” thick, but the actual thickness is 23/32” and will be listed that way at the lumber store.
IMPORTANT: Most sheets have a slight bow or “crown” to them. When setting them down, be sure that the crown is up. In other words, you want the sheet to make a hill, not a valley. If you do this, the weight of the entire platform itself helps remove any bowing from the final product.