Thank you both for your answers.
Beating Bonemass unlocks skellies to spawn in Meadows, not sure about greys. But I don't plan to defeat bosses in this particular world I just want to do some landscaping without having uninvited guests. I finally found a very quiet meadows with very low aggro levels. Just the eventual greyling that passes by from time to time.

If only I could tame necks that'd be perfect because they'd be able to patrol the area without me needing to tame pigs. I'm more of a lizard guy. But modding is a bit too complicated for me. I can manage to replace a few textures and audio and that's about it.