I know, if you had a workbench, you wouldn't be building a workbench. Even so, you'll need some sort of work surface, even if it isn't as stable or capable as a proper bench. The traditional solution is to throw a hollow-core door over a couple of saw horses. The advantage of hollow core doors is that they're flat, stiff, and cheap. I used a folding table and a hollow core door I had bought for a future project.
I live in VA and my workshop is an unheated, uninsulated garage. I work out there year round, even when temps are below freezing. I can't say it's comfortable in the winter (or when it's 100 degrees with 95% humidity) but I haven't had any major issues. I have had some big box green wood warp on me after I built a couple bookshelves and brought them into the house, but that was more a factor of the green wood than my "shop".
Flip the base upright, put the MDF on top of it, then use a straightedge to draw two straight lines joining the outside edges of the legs and extending the width of the MDF. I used the countertop as the straightedge. We cut it with our cutting guide, which is based on the factory edge of a sheet of 1/4" plywood, so it should be straight enough. Use a carpenter's square to transfer these lines onto the ends of the MDF.
The last thing is to semi-permanently attach the bolts for the vises. Given the amount of work necessary to get to the bolt heads, once the top is joined, I had intended to tighten them up so they wouldn't spin, and lock them that way with blue Loctite. (That's the strongest non-permanent grade.) That didn't work. What I found was that the bottoms of the countersinks weren't quite flat, and when I tightened the nuts down that far, the ends of the bolts would be pulled far enough out of alignment that the vise bases would no longer fit. In order for the vises to fit over the bolts, I had to leave the nuts loose enough that the bolts had a bit of wiggle - which meant that they were almost loose enough for the bolts to spin. So I put Loctite on the nuts, to keep them from unscrewing, and filled the countersinks with Liquid Nails, in hopes of keeping the bolts from spinning. I considered using epoxy, or a metal-epoxy mix like JB Weld, but I didn't have enough of either on hand. It seems to be working for now, though the real test won't be until I have to take the vises off.
Our programs prepare our students to open their own woodworking business or become employed by a high-end woodworking related business. We currently offer an Associate of Science Degree as well as a Certificate of Achievement in 8 different Program Areas. Students may also take coursework to complete a Certificate. Our courses range from Furniture Design and Instrument Making to Production Cabinetmaking.   Our graduates are highly employable with the diversity of courses available.
I wanted the left edge of the jaw of the front vise to be flush with the left edge of the top, the right edge with the left edge of the left front leg. So the amount of overhang on the left depends upon the width of the front vise jaw. The width of the jaw is, at a minimum, the width of the plate that supports it, but it's normal to make the jaw extend a bit beyond the plate. How far? The more it extends, the deeper a bite you can take with the edge of the vise, when, for example, you are clamping the side of a board being held vertically. But the more it extends, the less support it has. I decided to extend by 1-12", which gives me a 2-1/2" bite, and which should still provide solid support, given that the jaw is 1-1/2" thick. This means the top needs a left overhang of 12-1/4".
The book is well written and easy to read. The illustrations, I'm sure were excellent in 1914 and, are still adequite now. Most of the designs seemed repetitive, though. I wish more attention had been given to lashing materials. If you are looking for that you will find almost none here. The book was fun to read and provided enough inspiration to make my brother and me attempt a large hut.