For a long time, I wanted to build a team that included Kingambit or Tapu Fini, but couldn't come up with an original team that was up to my taste. Today, I just happened to try and build Full Room teams. I noticed how both these mons can performs excellently under Trick Room and decided to put them both in the team.
I like to build around a Steel / Fairy / Fighting core, so I decided to add Iron Hands next. Iron Hands is not only a strong physical attacker but a useful Fake Out user as well; it provides opportunities for its teammates to either use its setup move or set Trick Room.
Here is where Sinistcha comes in! While its teammates are using a setup move or setting up Trick Room, they are most likely to lose a good chunk of their HP. Sinistcha help its teammates to regain those HP via its ability Hospitality or its move Life Dew. It also serves as a redirector and a Trick Room setter. In short, Sinistcha is just a great utility mon.
I wanted another good, bulky Trick Room setter, and not one that was weak to Ground-type moves. (Reason being is due to the Mega that I would talk about later.) I thought Porygon2 wouldn't be a bad pick since its move Recover will allows it to be more resilient and perhaps, set up more than one Trick Room.
The last mon to be selected was Mega Camerupt, mostly due to its good coverage. Due its low speed it is the premier Mega for Trick Room.