Your Fabricator is essentially your base, and you’re going to keep on coming back to this to build more Fortifications and acquire better weapons. Therefore, at the very start of the game make sure to place your Fabricator somewhere on the map that’s easy to defend and can give you a good vantage point over incoming enemies.
The countdown to wave one won’t actually start until you’ve placed the Fabricator down somewhere either, so take your time to pick the perfect spot before settling in for the long journey ahead. If you find that you’ve placed the Fabricator in too much of a dangerous place, you’ll be able to move it later on. It’s best to get it first time though so that you don’t have to move all of your defenses as well.