My raised beds are on a bit of a slope. To level them, my husband secured a 2×4 horizontally to the bottom of each bed at the downhill side. He used three 2×4 stakes on each and left these sticking out a few inches at the bottom. One some beds where the slope was steeper, we left the stakes at the soil surface and filled in below with a layer of brick. For most, the stakes were dug in leaving the horizontal 2×4 resting at soil surface. One or two were on a flatter ground and he dug the whole horizontal board in a bit. We used brick to fill in at the sides. Now all of the beds are pretty much level. Next step – add dirt!