First your colonists are going to run out of oxygen, then water, and finally food. The further your colonists have to travel to get their resources, the longer it will take to build the structures they need to survive. Keep the Airlock close, to either the left or the right of the spacecraft. However, you will need it far enough away in order to eventually place a Landing Pad for Colonists, Trading, and Visitor spacecraft to land.
The mountain side is where you will be placing your Mining facilities, so you do not want it too far from your Airlock. Pick an area that is not too far from a mountain and your spacecraft and place your Airlock. If you do not think you have a big enough area, or if it looks like the base when constructed would be very convoluted, restart the game again with a different pair of coordinates. After you land and your crew exits the spacecraft, use the and keys to pan around and determine if you have a flat area large enough for your base. The coordinates (longitude, latitude) that you establish for your base will determine what the terrain will look like.
