A dice tray is container that you can cast dice into that will prevent them from rolling off the table or knocking game pieces. Ideally, it should have -
A relatively small footprint to not take up too much table space.
Walls that are low enough that you can pick the dice out easily but high enough to keep rolling dice constrained
Inhibit dice from landing on an angle ie not flat
Have soft surfaces to reduce the clatter of dice and reduce wear.
Commercial dice trays are available but always seem very expensive. I'm not looking for solutions that keep the dice always constrained as I want to be able to choose to throw different amount of dice. I'm aware there are many dice simulator apps but they don't handle all non-standard dice (eg. symbols rather than numbers) or work well in bright sunlight and just aren't as visceral.
Update
Thanks for the ideas. I've actually gone with an idea I found on the web after asking this question here. I bought a cheap deep box frame (like a picture frame but can hold 3d objects e.g. seashells mounted on a backing). I then glued a piece of felt directly to the backplate and remove the glass. I stuck some bits of felt on the rear, now underside, to act as feet. I'm very pleased with the result and it looks good too.