This will give you a nice position for the telescope. If you don't like it that high, it's easy to make it shorter later on. Then drill nine holes within these lines. The screws to attach the side boards and front board will come back UP from underneath to attach these pieces to the base board. When everything is properly fitted, assemble the rocker box.
Test fit the curved sections of the side-bearing box to the telescope tube.
They should be a bit loose and slip around the tube easily. If they aren't, you will have to remove material and sand them until they are. Later you will attach felt to these curved sections. They must be fairly snug when the felt is attached. Refering to the plans and diagrams, assemble the side-bearing box.