The first step in building the Y stage is finding all the components that are needed. They give you a picture of what they all look like here:
I wish they had put all the components needed for each sub assembly together in one plastic bag. It would have made it much easier and given me confidence I had the right pieces. In my bag marked "Build Surface Kit" it had the Build Platform wood and Orange Makerbot plaque but it only had 5 magnets, 6 nuts, and 6 screws. In the picture they provide there are 10 magnets, 12 nuts, and 12 screws so it's not clear if I am missing pieces or if I am supposed to mix and match from the different bags. To add to the confusion the picture has 12 of each but the bill of materials calls for 6 of nuts and bolts.
6 M3x16 bolts
6 M3 nuts
Despite the ambiguity I just dug in and started building. About 30 minutes later I have this to show for my work, a completed Y Stage: