My
Blood N Bones base. It's a very difficult modpack, and I play it in hardcore mode, so the base is less about aesthetics and more about efficiency and progression.
My starting base usually looks like this. Basically a long underground tunnel (60-100 blocks), which lets me exit the base in the morning at a place where most mobs have despawned. I start digging it on the first-second night.
After I gather some resources and make metal armor, I pack everything and look for a better location for a permanent base. That's a plains-type biome, on a flat spot (for easier terraforming) with no nearby towers.
A 3x4-chunk surface area is generally enough for anything I need. The walls need to be 2-block thick, otherwise giant zombies are spawning in the walls and glitch into the base. The mobs also need to have a path into the base, otherwise the AI seems to be causing massive lag. A quicksand trap that is two blocks high with a sludge channel underneath is a great early mobgrinder, which provides plenty of gunpowder, arrows and bones. Later I upgrade it with the MFR grinder.
Another neat mobgrinder is this Cinder trap. I think I first saw the concept in Ssundee's videos. I think there needs to be a minimum amount of fires for constant spawning, 8 seems to do the trick. I think it also needs two solid blocks between the fires for some reason. I make one immediately after the first trip to the Nether, so that it grinds enough stuff over the course of my entire playthrough. And a later MFR grinder upgrade of course.
My streamlined sandwich kitchen. Every table has specific tools to make each ingredient, and the chest contains neatly arranged fruit. This lets me make a full set of 9 stacks of sandwiches in seconds. I also have such a table for Needlegun ammo.
Smeltery area. The high oven gets obsolete very fast, but it's still great for making clear glass fast. That Cinder grinder provides 3/4 of the Pyrotheum ingredients for the induction smelter, it doubles the ores and produces Rich Slag for tripling the rare stuff.
And of course, the dragon kill. 1300 Dragon Essence and 144 levels.