Other people have written better posts about why fullroom is struggling right now, so I won’t go over it. But as a ladder rando, I miss my funroom. It's not the most creative archetype, but it's been fun so far.
Starting point: if you’ve laddered recently you’ve been 6-0’d by Beat Up. I wanted a follow me user that could stand up to Terrak (and Melmetal, RIP Indeedee). Babiri Togekiss gets murdered by both, but Home gave us a new Follow Me user who also has Fake Out - Blastoise. The big guy seems hard to OHKO for most common mons, and if you don’t want to Follow Me or Fake Out you can start clicking Yawn or Scald. I’ve been pleased with how well this works, and would encourage better builders than I am to try it.
Home also gave us Necrozma, and I wanted to try it out in this meta as a TR setter, since Hat got Parting Shot out of its spot at the top. Weakness Policy seemed like the best call here - Necrozma wants the offensive help for neutral mons and it has Solid Rock Lite. I find myself maxing Necrozma a lot more than I thought I would when building.
I like CB Melmetal a lot on this team - I started out with AV, which can live an obnoxiously long time, but I found myself wanting more immediate damage, and not valuing the AV bulk as much. CB Melmetal also seems like it doesn’t really want to Dynamax, which Necrozma really appreciates. Torkoal deals with other Melmetal and Corviknight, while providing a consistent source of spread damage.
The last two I was less sure about. Conkeldurr got buffed with Knock Off, while providing a second physical attacker. I found it to be a solid cleanup mon. In the last slot, the things I want are: Taunt, a way to trigger Necrozma’s WP consistently, and another Trick Room setter. I went with Mimikyu, and it hasn’t been awful - it can eat the occasional Dynamax hit and pretty consistently gets TR up when it needs to. Mental Herb has never done anything for me, but I wasn’t sure what else to run tbh. Just remember that Melmetal can and will OHKO it if you don’t have Blastoise to Follow Me. I tried Goth here, but the lack of Shadow Sneak felt really bad.
Details:
Blastoise's EVs survive 252 LO Plasma Fists from Zeraora, and the rest is put into speed because sometimes you want to outspeed a Fake Out from Heel Cat. We’re 54 EVs short of always outspeeding a 252 Jolly Incineroar, but if they’re running that and do the perfect lead, they're welcome to have the win.
Mimikyu running Relaxed hasn’t done much, but I do think you want low speed to be totally sure you underspeed and Taunt Mew, which sometimes acts as an Anti-TR bandaid mon.
Other EVs are probably suboptimal.