You cannot adjust density in the game the way you can with designing a POI, so you will have gaps like that. POI designers set density around the terrain and block transitions to get it smooth. If you want to avoid it at your base, you can place a plate block over the gap to hide it.
As far as why.... Terrain is a tetrahedron shape (I think that's the right name) and blocks are cube shape, so they didn't fit together perfectly.
I tried the hoe mod a while back. It's a great idea and does make a difference. The gaps aren't nearly as stark, but it still doesn't bring the ground perfectly level with the building block(s). There's still a bit of a slope/gap between. The plate technique is still the only solution for perfect leveling, afik, despite that it just covers up the gaps. Both might be tried together, but I just went back to the plate technique myself. I figured there was no sense in leveling the ground if I was just going to have to cover over what I'd just raised with the hoe.There are mods that let you adjust block density in game. I keep meaning to try this one by OCB as it seems the most intuitive of the ones I've seen (you use a garden hoe) but haven't gotten around to it yet. Updated for 1.0, from the comments some people can't get it to work, others it works fine.
https://www.nexusmods.com/7daystodie/mods/2806
Also, if you use the sheet block instead of plate block, it will appear flat rather than being raised up. It has far fewer hit points and so can break more easily, but it isn't likely much will hit it anyhow, and it is just decoration, so not a big deal. There on some paint to already blend into whatever terrain you have and it isn't horrible. Not perfect, but not bad. It just ignore the gap and you will get used to it before long.I tried the hoe mod a while back. It's a great idea and does make a difference. The gaps aren't nearly as stark, but it still doesn't bring the ground perfectly level with the building block(s). There's still a bit of a slope/gap between. The plate technique is still the only solution for perfect leveling, afik, despite that it just covers up the gaps. Both might be tried together, but I just went back to the plate technique myself. I figured there was no sense in leveling the ground if I was just going to have to cover over what I'd just raised with the hoe.
I used the sheet block the one time I chose to level a pit, but couldn't find it the last time I looked for it. Will have to remember to search for "sheet."use the sheet block instead of plate block
Just a tip... If you want to level ground (doesn't fix the edges around blocks), take a building block and drop it on the ground and pick it up again. It is very fast and easy and doesn't require a mod or dev tool. This works with any block, but is easiest with that one since you can pick it up again without breaking it.I used the sheet block the one time I chose to level a pit, but couldn't find it the last time I looked for it. Will have to remember to search for "sheet."![]()
Also, to clarify, there are other uses for the hoe, e.g. leveling the ground a little around buried farm plots and such. Don't want to give off the impression it's useless because it isn't. It's a great mod. I just don't use it anymore myself.