The edges of MDF are fragile, easily crushed or torn. MDF is also notorious for absorbing water through these edges, causing the panels to swell. In Sam Allen's original design, he edged the MDF with 1/4" hardboard. This edging is one of the complexities that Asa Christiana left out in his simplified design. I think this was a mistake. MDF really needs some sort of protection, especially on the edges.
Lay a leg flat on your work surface, with the countersink side of the thru-holes down. Stick a piece of threaded rod in each hole. Take a stretcher that is marked to have one end adjoin the top of this leg, stick a dowel center in its dowel hole, line it up against the leg, using the threaded rod for positioning, You want the top of the stretcher to be even with the top of the leg, or just slightly above it. Give the end of the stretcher a whack with your rubber mallet. This will leave a mark indicating where the matching dowel hole in the leg needs to be drilled. Repeat with the lower stretcher than adjoins this leg. Then repeat for the other leg that will form this trestle, and the other ends of the two stretchers.
I was raised by crafty people. In every sense of the word. Just kidding! My parents were lovely people who loved to work with their hands in their spare time. For a brief period of time as a kid my mom even earned a living by selling her wares at local craft fairs, but for the most part their crafting was a hobby that filled our home with beautiful and practical pieces of woodworking.
Another odd design feature of the Windsor Design is its dog holes. While this bench provides a variety of dog holes and even offers numerous pegs and dowels to go along with it, the dog holes are not spaced as closely or with as much variation as you see with many other benches. Ultimately, this means that smaller workpieces may not be able to use the dog holes and pegs as well.