Need 18x20 wooden base

I've built a few bases that size. I usually use 3/8th-1/2" plywood (whatever scrap I have in the garage). Cut to size, then I'll frame it in with trimwork (usually door trim from HD). A simple square base is easiest, just 45 the corners of the trim. Some bases get covered with static grass, some get covered with sandpaper (for concrete/tarmac. For the sandpaper, I buy a pack of 8 X 10 grey paper. Spray the wood and back of paper with sprayable(obviously) contact cement. Allow that to dry for a few minutes and stick the paper to the wood. I'll then randomly spray a couple shades of lighter grey to vary the surface a bit.

For this example, I used drywall plaster to vary the terrain a bit, and to simulate the concrete.

This one is sandpaper, and HUGE!!! That's a 1/32 A-10

 Static grass

 And a closer shot of sandpaper base. I cut the paper down into squares, whatever size I want each section. I paint the "expansion joint" black, and sometimes through in a few weeds. For the oil drips and stains, I mix up a bit of black and brown enamel, thin it way down, dip the brush in it, then flick it at the "concrete". For bigger spills, just touch the brush to the surface.

 One other option that I can think of (if you have no woodworking skills), would be a cutting board. I know they are many pieces of wood put together, but at least they are more pleasing to the eye than regular plywood would be.

You might check with your local cabinet shop(s). They often have veneer plywood scraps left over from jobs, and can cut a base to your size and edgeband it with the matching species. It's a much cheaper route than ordering and paying shipping. Fermis' cutting board idea is also good, and the home centers usually also sell laminated (edge glued) rounds and "planks" which can be stained and clearcoated for a wood display base.

mike

stcat

Putting together a DC-6 for a presentation and looking for a decent walnut base.  Can do the Home Depot route but the wood is 3 ply, which means edging will be a different grain.  The decent wood they have isn't wide enough, which means visible seams, and this model will not have a runway, just the wood base.

Has anyone ordered a custom quality wood base of large size (18x20), and if so, could you tell me the source?

You can always give Michaels or a shot. Check their frame section for 18x24 frames with or without glass. You can substitute the cardboard picture backing for foam board also available there. You can airbrush the foam board as a Tarmac and frame it as you would a picture.

Home made Tarmac on a white foam board and set on a picture frame.

You can get a roll of wood veneer in about any home improvement store...   Just cut your base to size, then glue the veneer onto the edges...