Set the 48-by-48-by-3/4-inch medium density fiberboard on a work table along with the piece of 1/4-inch lattice. Put the 72-inch straightedge on corners that are catty-corner from each other on the fiberboard. Draw a line from corner to corner. Repeat this with other two corners to mark the center of the material.
Drill a hole through the lattice 1 inch from one end with the 1/16-inch drill bit. Measure from that hole, mark the lattice at 24 inches, and drill another hole in the lattice. Place the first hole on the center point of the fiberboard. Insert a box nail into the hole and hammer it in just enough to hold it firmly.
Insert a pencil in the other hole and draw a circle around fiberboard. Cut the circle out with a band saw or jigsaw. Sand the cut edges with a piece of 100-grit sandpaper. Install the casters around the circumference of the circular bottom of the crib according to the manufacturer’s instructions.
Place the piece(s) of the circular rail on the cutout. Mark the center of the railing between the outside and inside edges. Make a mark every 3 inches to indicate where the spindles will go. Drill holes on every mark 3/8-inch deep with a drill bit that matches the dowel at the end of the spindle.
Put a drop of glue on the end of one of the spindles and insert into a hole. Drive a finish nail through the railing into the spindle to hold it in place. Repeat this process with the remaining spindles.
Position the spindle assembly on the medium density fiberboard bottom and trace its pattern onto the bottom. Drill pilot holes through the railing with a 3/16-inch drill bit every 18 inches. Remove the spindle assembly, apply glue to the circumference of the bottom and secure the assembly to the bottom with the wood screws. Clean up the excess glue with a damp cloth.