When I went to my first couple of launches, I noticed that a lot of people had stands to hold their rockets while they prepped them for flight. There were metal and wooden cradles that worked well. I also saw a PVC cradle that looked easier for me to build.
PVC pipe is easy to work with. It is like putting together tinker toys (that reference dates me, I know). As this rig will not be holding any water pressure, buy the PVC glue that does not need a primer. That eliminates a lot of the mess.