I have found that practicing systems at home has been very valuable for me. I like to use chairs, sometimes you need to add weight so they don't tip over but you can place them wherever you like and attach carabiners in different configurations and practice building different systems. In the following video you can see I have three carabiners on a step stool and then I have a fourth on another chair. The anchor that I demonstrate is a pre-equalized anchor in a series.
Keep in mind the sole purpose of this is to demonstrate how you can practice at home. The video doesn't show angles properly so it may look like the fourth piece comes in at a 90 degree angle. This is not the case. Further, we'll assume that in the field I would lock all the carabiners and use the appropriate carabiners at the master point, etc.
--Tim Page, Program Coordinator and AMGA Single Pitch Instructor