The first step in the process is to knock out about 36 plywood discs. The discs I made are 3-1/2" in diameter but you can make them any size you'd like. Each disc has a 25/64" hole in the center. The hole is slightly oversized to allow a 3/8" dowel to slip through the center to help align all the pieces.
I used to make the discs with the circle cutting jig for my plunge router shown in the attached pic Fortunately I live in the Bay Area and I now make these at TechShop with the help of the CNC ShopBot. I can now knock out the 3 dozen discs in about 30 minutes of machine time. I also recently assembled a sled for holding the log which is a great help in the upcoming slicing step.
Once all the discs are cut start slipping them on to a 36" length of 3/8" dowel. Don't be shy with the wood glue in between layers. Squeeze them all together with 2 pipe clamps. The extra length of dowel gives you something to hold onto when your cutting towards the end of the log.
When the glue is dry it's time to sand. A benchtop belt sander makes pretty quick work of this but it can by done with a handheld small random orbital sander. Doing it by hand always reminds me how much sanding has become my least favorite part of any project.