Right now, there is no schematic. When there is a schematic put on this page, you will need a program called McEdit to put the schematic into your world. Once you have installed McEdit, download the schematic and put it in the "MCEdit-schematics" folder where your McEdit is installed.
  Now, before we install the schematic to your world, you must make sure (x=0,z=0) doesn't have any mountains over y=150 make sure your player is around (0,0). Now, save and close Minecraft and run McEdit. Open the world you want to put the schematic. Now click "Import" which is on the hotbar. Click on the UHC Box schematic and place the box in a range between (x=±45,z=±45) on the surface. Make sure the box doesn't excceed over y=150. Save the changes in McEdit and close it.
  To make sure, open the world in Minecraft and press "f3" on your keyboard to get coordinates. Now make sure the box doesn't go over (-45<x<45,surface(Usally y=65)<y<150,-45<z<45).

  As it mentions, this is a customizable UHC box, so there has to be a setting room. In this room, there are different buttons and levers. At the top, it will state what is the setting. At the bottom, the list of options for that setting. Here is a list of all the settings and what it is set to default:

Worldborder Size (Default is 2000 by 2000)
- Daylight Cycle (Default is set to true)
- Shrinking Worldborder (Default set to false)(By default the worldborder will shrink to 200 by 200 in 3 hours disregarding           worldborder size. RECOMMENDED to change if worldborder size is not 2000 by 2000.)
- Teams/Solo (Default is set to solo)
- Weather (Default set to true)
- Difficulty (Default set on Hard) (Options: Normal or Hard. This is ULTRA HARDcore. Don't expect easy lol.)
- Is the host playing? (Default set to true)(The host is hosting the server and may be not interested in playing, but watching and recording it all.)

The host that will be in creative mode, can change these settings to his or her liking or for the occasion.

  When the settings have been configured, teams will be arranged. Teams have to be even as possible. If you want random teams, select the size of each team or how many teams you would want, then whenever ready, press the start button.
  If there is an odd man out that is not on a team,don't worry! The first team to find a player in-game without a team, gains the player and adds them to their team.