I made some similar things to do the floor in my ute. I used a press, but some things i learned
i made 2x square 19mm plywood, with the same size hole in each of them. With plenty of overlap for the panel (2 or 3 times the diam of the circle) and zinged self tapping wood screws all around the edge. This helped a lot to keep any wrinking of the surrounding flat to a minimum.
Then i welded a few pieces of 10mm steel together and spun it in a drillpress and shaped it with a grinder to make the correct floor shape, i made this maybe 2mm smaller than the hole in the bucks
as you will have a hole in it to do this, what you can then do is drill a hole dead centre in the sheet metal you are shaping. without a press, you can put another plate of 10mm steel on the other side of your wooden bucks and using a greased up bolt, ugaduga the two together. 1mmis steel will shape really well this way, and might save you some elbow with the hammer