Building a bench starts with choosing a design, which can be confusing and/or overwhelming due to the multitude of info/books written about different benches. Bench height, vise placement, round vs. square dog holes, size and thickness of the top etc. are all considerations. Experience is invaluable here. If this is someone’s very first bench, my advice would be to build something cheap and simple, use it for a few years and decide what you like and don’t like about it and base your ultimate bench design on it, rather than picking the shiniest roubo design and building it based on what others have said you need.
My first bench was a simple design from FWW made of plywood with a small front vise. When I eventually had the time and money to build a real bench, I knew what I wanted based on my experience (thick front apron, small tail vise, bench as thick and heavy as I could make it, no tool well, no sliding deadman etc.)
Rob, Sault Ste. Marie, Ontario