So, I've been playing some Hardcore, lately (okay, just Sunday.) I look forward to getting back to filling sky, but I just wanted to futz around on the seed "Hardcore" in hardcore mode, just to re-experience how hard it is to start from scratch, see what the seed was like, and so on.
It wasn't bad; I spawned on a heavily grassed plainy area with lots and lots of cows around and many trees. I immediately dig a two-deep hole and push a couple chickens into it, then gather some wood, till some land and plant some seeds, and hide in my hole at night. I tried mining stairs downward but found a maze of abandoned mineshafts that didn't have a convenient chokepoint approach. So I decide to heck with it and just relax with my chickens, using their eggs to increase their number (and trying to keep them from going down the mine stairs; eventually I work out an arrangement of trapdoor stairs that I can fold flat to make them useless when I don't need them.)
The next day I explore across the nearby river and find a ravine with lots of exposed iron in it! Whee! I route the river into the ravine and swim down to the iron, gather it, one thing leads to another, and I end up moving there.
I now have brought grass to the bottom of the ravine and terraformed it so it's pretty and the waterfalls look natural. I've got some wheat and sugarcane growing there, and I've got several scattered beds that I've made with the spider string from my spider dungeon grinder. This, because we (inexplicably) can sleep ANYWHERE as long as we go to bed before monsters show up (I hope this is changed.)
I've played it safe. My first three iron ingots became a pick, but the subsequent ones went directly into armor. The sword was later...and I'm always fully fed. Eventually I'll start carrying golden apples, but I'm not really wandering into harm's way.
At the very bottom of the stairs, where it hit bedrock (I have to go to bedrock so I can count upward from the top layer and know my Y coordinate; I'm not using F3) I build a large clear room with smoothstone walls and floor (floor is easy; mine out all the non-bedrock on layer six, fill with water, then pour lava on the water to make it turn to smoothstone. I like the patches of obsidian and bedrock so I leave those in; otherwise I'd make the floor a meter higher. ..which would be easy, and cost no resources!)
I wanted slimes to spawn there, but they don't and I have plenty of slime from my other explorations so I don't really need them. I instead lure cows down there and make them breed. The bottom step I replaced with a trapdoor so that cows (after I bring them down into the ravine without killing them and then bring them down the stairs to bedrock) don't wander back up the stairs and hurt themselves.
Later, to make use of the AFK time I spent sleeping without having to go way back to my chicken hole, I built a new chicken hole off one side of my staircase down. I make sure there's a dent in the wall under the ladder so that the chickens won't jump up and climb the ladder out, and I stand in there with a dozen chickens and let them push me around and fill my inventory with eggs. This is very safe.
or so I thought. Dun dun DUN!