I like to be able to tweak size and shape even after building a raised bed, so I use movable walls. Concrete paving stones stood on end, leaning in agaunst the soil.
At only $0.95 to $1.30 each, they may even be cheaper than some wood designs. And they couldn't be any permanenter!
3/4" x 8" x 12"
1" x 12" x 12"
By swapping one kind of oaver for another, or stnding the 8x16 ones up "the tall way", I can even change the depth of beds, especially on a slope.
And you can lean them away from the soil to check for and destroy slug eggs, or add or remove a plastic liner to change water retention.
