I marked the holes by putting a dowel center in the end of a long piece of 1" dowel. Run it through the holes in the base plate, and bang on its end with a mallet. Rotate it a bit and bang it again, and repeat. Odds are the dowel center won't be precisely in the center of the dowel, so you'll be making a small ring of marks. The center of the hole is, of course, the center of that ring.
You may even want to put yourself in the picture. If your workshop space already exists, find a large piece of cardboard, wallboard, or plywood that’s about the size of the workbench top you envision. Find a couple of stools or chairs, perhaps a few books, and turn them into stanchions to support the “benchtop.” Is it too big for the space? Is it large enough for the tasks you envision will be performed upon it?
Traditionally woodworkers (joiners) learnt their craft working as an apprentice in the Master Craftsman's shop doing the grunt work and learning by assimilation over many years. Our approach is a little different. We're making the assumption that you're smart; are developing or already have a passion for woodworking; and can devote three months to intensive learning.
Post Woodworking’s Hampton shed is a major standout in design. The sleek farmers porch immediately draws the eye into its pure New England charm and provides the utility of shade and a cool place to sit and enjoy a cold one. Like all of our sheds, the six-panel doors which add to the structure’s aesthetic come standard. They’re made out of fiberglass to last through many decades out in the elements.