I used cereal box cardboard for templates. I took off the radio bezel trim piece and traced the flat part above the radio, that was my base.
Then I made another template that was the same size of the base of the store-bought cup holder, but also, I made it follow the dash trim piece that goes from under the "storage tray" thing to the instrument panel.
Then I made vertical braces that contoured the rounded dash trim piece (from behind) and connected the front edges of the 2 base pieces (towards you).
Then I crammed floral foam between the 2 bases and rounded the front of the whole thing, then lined the entire thing with foil and laid a few layers of fiberglass on top and when hardened, removed the inner foam.
Then I did a lazy bondo job to smooth it out, could of spent more time on it, but I wanted to use it!!
Then I drilled 3 holes along the bottom base and transferred those holes to the flat part of the dash above the radio, then drill them out as well.
I put bolts through the holes and welded the heads to the bottom brace (You cant get to them when its on the dash) and bolted it to the dash for good.
wha-la!!