I noticed some discountinued flooring at my local big box store and saw the opportunity for a new bench in my future. It was relatively inexpensive and easy to do. Plus it looks like a bowling alley, how cool is that???
Look for the solid or real engineered version. In my opinion it will give you the best work surface and will last the longest of the options I found. For the small area of a work bench it really does not take that much material.
I opted to go the cheap skate route; my usual modus operandi... I looked that the local flooring stores for close outs. They had the best price per foot but wanted me to buy whatever they had left, which was usually 2 or more boxes more material than I needed. So I started looking at the home stores and big box retailers. Eventually I found some on clearance. It was solid bamboo for about $15 a box. I bought three but could have gotten by with 2. Yours will vary. My bench is 2' by 22'.
You can use what ever wood you have laying around. I did not have enough of any one type to get it done so I bought some 19/32" sheathing plywood. I think it was about $17 per sheet. I needed a little more than 2 sheet so had to buy 3.
I put a cleat around the edges to use as a ledger. I used a combination of 2"x2" left over from another project and I ripped some 2"x4" lengthwise for the rest.
I used a combination of deck screws and misc screws from my misc. screw box to mount the ledger and attach the base to the edges.
For attaching the flooring to the top I used construction adhesive and a brad nailer.