Cant really help with the slot suggestion, but I can make a few other...
First, if you do slot it as I am imagining, be carefull not to go overboard and weaken the table.
Another suggestion is to maybe incorporate an area for cutting. The neatest one I see, and was simple, was just a hole in the table maybe 2' x 2' and it just had bar-grate in there. That way, you could lay the peice flat and cut and not have to worry about burning through the table. And it gave all the slag a place to fall away. If I ever make another welding table, I think the WHOLE top will be heavy bar grate. and the openings in bar grate are usually large enough to drop a c-clamp in:thumbsup:
Another suggestion (an we have this in our shop at work) and it may be a lot more work than you want, but we have a metal post mounted on the wall for hooking the ground clamps to. And then a heavy guage cable laid in a trench in the concrete and attached to the leg of the table. One less cord to worry about running over and getting tangled.:thumbsup:
And I cant really help much with the electrode holder
But I wouldnt want to use wood on a welding bench. They might not last very long:laughing: