We have numerous benches we have made from a 50 x 50 frame with 10mm/12mm plate top. Some have box section or angle welded to the top for various jigs.
We also have a huge t slot table which is 120mm thick - it weighs 12 ton, but cost us 100 quid at auction. cost four times that in transport. They could drop the bomb and it would still be there untouched!
If its an odd bit at home, i use a cheapie workmate jobbie, witha bit of plate ontop. A bit of box tacked to the plate clamps up in the jaws to hold it steady.
I either use the floor, a wooden bench with a bit of paving slab on top or an old pallet set up on blocks, treat this as more or less disposable and change the pallet as required, this one works best for me, or just in the vice for small things.
if you are only doing a bit of welding plate the top of the bench with a sheet of 3mm
benches I used to have in my workshop were 6x3 10mm sheets on a frame made from 80 x 80 x5 bolted to the floor as they were used a lot and you could tack things to it them and modify with 14lb hammers.
fastern your earth to the sheet on the top and you dont have to wory about bad earths.
if you are between you could make some thing like I made in my dads garage when I was at school. this is stil there 15 years later it is 50mm box with 5mm plate top.
We also have a huge t slot table which is 120mm thick - it weighs 12 ton, but cost us 100 quid at auction. cost four times that in transport. They could drop the bomb and it would still be there untouched!