level off, pare down, raze ground
剷 centers on cutting or scraping something down to make it flat or even: leveling off, paring down, or razing ground.
剷 combines 産 (produce, give birth) with the knife radical 刂, suggesting cutting or scraping away to produce a level surface. The exact historical development is uncertain.
The left side 産 suggests something produced or built up, and the right side 刂 is a knife. Imagine using a knife to pare down a rough surface until it is level and smooth.
For サン, picture leveling a sandy surface with a knife: sand -> サン, and the knife scrapes the sand flat.