Methods we have figured out for newborns.
For awhile I was just holding the baby over the sink. He got heavier and that wasn't easy even when he was little.
I ordered a potty seat hoping to find a way to make it work even for a seven week old baby. It is too big for now. Cold and disruptive. We have it for later though.
So lately what we have found to work is to just lay him on his "changing table" which is just the counter in the bathroom with a towel on it. Then when we take off his diaper we put a washcloth over his penis to collect the urine. We place a rag under him to collect the poop. And, if anything leaks it just goes on to the towel under him and we get a dry one for next time. No big deal.
So far this works great. No one has to hold him so we don't get tired if it takes a little longer. Everything is there and ready for cleaning up. It is in another room, specifically the bathroom, so he gets used to the idea that eliminating usually takes place in another area.
This is the method that has worked best for us so far.