The bases aren't essentials for survival but are really useful. To build a base you need some items.
Items needed Edit
Blank Blueprints (can be found or bought) AND Base Blueprints
Split Log / Stone Pebble (depending on what you use to build your base)
Split Log and Stone Pebbles can be bought, but split logs can also be mined from trees with a hatchet or Fireman axe and stone pebbles can be mined from stone with a sledge hammer or a miners pickaxe.
The Base Center is very quirky, in that it requires less space if there is only stone, grass or tall grass nearby, but if there is any other block nearby, it requires more space. The space requirement is (If dirt/stone are the ONLY thing within 17x17 and 6 high) 11x11, and 4 blocks free above it (5 blocks out from the center in all directions). But If there is anything (as far as I can tell) other than stone, or grass under the 11x11 cube, it will not work. The base will usually require a 17x17 area (9 blocks out in all directions from the base center), and 6 blocks free above it. Tall grass does not affect a base. There is also an item in the game that may be in the maps, that causes you not to be able to place a base for a large radius.The leaves and glowstone represent any block.
The first picture on the right is a century.
The Second picture on the right is also .
The Third picture on the right does work even though it is .