When you get started, especially if you're not the fabrication type, try doing a cut and clean job on a piece of scrap first.
Gordon's idea of working with duct metal is a good one for someone who's done it before, but a decent 4' by 8' sheet of 16-gauge aluminum is only about $100 or so.
"Only," a hundred bucks is relative, but there's enough width to make the entire apron piece (the side-to-side measurement won't exceed 48" at any point) and any other fitment pieces all out of the same sheet with plenty of fudge factor.
It is imperative that you get good with heavy-duty scissors and cardboard first. The cardboard will allow you to make mistakes, fix them and move on to another template without cutting up a bunch of good metal. Transfer your lines directly to the aluminum with a Sharpie, and erase any fudge lines when you're done with red Brakleen. For corners that need to be rounded, use the top of the Brakleen can as the curve template; you'll be able to follow them with the jig saw.
Tools will include that jig saw, an air line and compressor, a hand-held pneumatic wheel that'll hold a Scotchbrite pad, a load of flat cardboard, duct tape and one Sharpie. I'd suggest using the Scotchbrite disc on the top and bottom of your cut edges to reduce burring, and then a perpendicular buffing on the cut edge to smooth that out, too.
It's not as hard as it seems. Just fiddle with a small project first.
If I can do it, anybody can. Good luck!