You could do the same thing with aluminum sheeting too, I opted for UHMW as it is nicer to work with (I think), and has more strength, slides over stuff easily (compared to other products like steel, aluminum) and has really no maintenance.
I'm gonna guess you'll need 4 square feet of UHMW for the rear and nuther 3 for the front. 28" of aluminum 1/2" angle for the rear and same for front. Big head pop rivets 20 for rear, 20 for fronts, 4 u-bolts for rears and 2 small bolts for front.
I bought a 4' by 10' 3mm thick sheet (UHMW) along with enough 9.45 mm thick material for skid plate over a year ago now and I wanna say (guessing) it was just under $500.00 CDN. Not sure what UHMW costs now, I know here in CANADA it'll be..... Oh twice the cost compared to lower 48
and guessing 4 times after the wall is built....
If you have basic tools, scroll saw, drill, pop rivet tool it's pretty straight forward to construct. I'd rather buy the tools and fumble something together as it's an opportunity for me to learn, plus I get more tools for other projects.
jrc