The most natural way to place a semi-solid platform may be to set it directly on the ground. In some cases (especially when working in the Super Mario Bros. 3 style), this works well. For the dirt hill platforms in Super Mario World style, this results in awkward-looking hills.
Increase the height of the platform by one block, then move the platform lower by one block. This gives it a more natural appearance, as seen in the level Yoshi’s Island 2.
This aesthetic is used in various locations in Super Mario World, including in the underground Vanilla Dome 1.