I'm a knob and would use 4 triangular pieces.
A much easier and faster route would be to run a trough down the middle and grade two strips of ply. A few kleats on the frame, liner and you're good.
Any type of grate would work, cut to size. Few pieces of angle iron. ReStore's and scrapyards.
I don't know. There is a convenience to a table. I just tend to build rather than buy. My time is cheap and it typically costs less or similar with a substantial difference in quality.
I'm invisioning myself covered in glue and chicken wire with a shit load of scraps from the dump around me , calling a grow shop for a table ... Lol... I wish I was handy .., all I can do is use tape