[Psalm 73]

I buy three 8 ft 2X10s (untreated) and cut one in half - nail 'em into a box and you got an 8x4 ready to go.

I dig down about a foot and place the box on it - no liner.

I make my own soil - keep two 4x4x4 chicken wire compost bins in the way-back - fill em' with ground-up leaves, coffee filters, egg shells, etc (and some horse manure) - this is what goes into the box gardens - takes about 6 months - rich and black, full of worms.

So right now the soil is about 5 inches below the top of the 2x10, so that gives me about (hmmm, 10 - 5 + 12), about 17 inches of soil - drains just fine.

The untreated wood lasts about 5 years, or so - when it rots through just nail another 2x10 in - nuthin' fancy.

[Tilted Irish Kilt]

Thank you both for the information about your "raised bed" gardens ! Very inciteful for ease of care and productivity.
It seems the best garden is to keep it simple, use compost manure, and fertilizer, and get to a decent depth for root crops.
I appreciate the comments about expected longevity of conventional wood , as well as what other materials can be used .