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.
Remove the jaws and route the edges that you could not route while they were still attached. Then use a roundover bit on all of the corners except the inner edge of the inner jaw of the end vise. Give everything a lite sanding, and apply Danish oil to the inner surfaces of the jaws. (By "inner surfaces", I mean those surfaces that will not be accessible when the vises are assembled - the inner surface of the inner jaw, that bolts to the bench, and the outer surfaces of the outer jaws, that bolt to the vise plates.)
As I was handling the 2x4's, during the routing, I realized that I really wouldn't be happy with the look of the bench, if it were made from these unfinished boards. They had stamps, pencil marks, and more importantly, incipient splinters left by the saw, none of which I wanted. And I was remembering what other shop furniture made from unfinished pine had looked like, after a few years in the grime of a shop.
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.
From the source tutorial, you can get illustrates to the instruction about the plan. Everything is fairly described as diagrams, images, the list of supplies and tools need etc. The process to this plan is very easy to understand and follow for if you are having some basic woodworking knowledge. Make sure to collect all the supplies you need before you start with the project. You may even ask any question directly in the comment section of the tutorial post and also comment the images of your final product if you have completed it. Either way, I hope that you will manage to build this one nicely.​
“With Hammer in Hand” by Charles F. Hummel (UP Virginia). Resurfacing like Brigadoon, the woodworking shop of the Dominy family was sealed up with the tools still on the benches and saws still sharp. Moved to the Winterthur Museum, the workshop is an open portal into village woodworking in early America. Hummel’s book takes it tool by tool, piece by piece, expanding our view with a true scholar/craftsman’s eye.

Skirting tradi­tional woodworking – sometimes seem­ingly allergic to it – this book shows you things you didn’t think were possible with wood, and many things you wish you had thought of first. The variety of the finished pieces is won­derful and makes for a nice read. Including 89 artists in total, each brief section con­tains background information, inspirational thoughts and technical details on how each artist completes their work. Wood Art Today 2 covers furniture, turnings, boxes, sculptures and more. One of the things I like most about it is you can open it up to any page and start learning about a specific artist and the work they do. This one is a lot of fun. 
Still, one of the best features about this woodworking bench has to be its vices. First off, the Sjobergs provides two vices both as sturdily constructed as the bench itself. The same hardware that fastens the bench works to ensure the vices are just as strong. The next main benefit on the vices in the inclusion of multiple positions – four in total – for the vices to go. This allows you to mix and match to suit your needs and allows the table to be used just as easily by right-handed and left-handed users.