If I had a rosary for every time I made a PSA on how to unlock a bench in , I'd have two rosaries, which isn't a lot but it's weird that it's happened twice. While the was a pain in rummy noble the thorax, the Sinner's Road is a different beast entirely.
This area (filled with terrible dogs) does have a bench smack-dab in the middle of it, but it takes a bit of fixing before you're able to actually kick your feet up. The route you'll need to take looks a little like this:
Make sure you've got 60 rosaries before starting, ideally secured in the form of a consumable string or a necklace. Start at the halfway home bench, take the elevator, then hop across the rickety platforms to get into Sinner's Road proper. Dodge the dogs in the long hallway (you can use the cages to avoid most of them) and then arrive at the central chamber.
Rather than going straight to the right, wall-jump up and head into the rummy satta room marked on the map above. Work your way across, dealing with bugs and jumping puzzles as you go, until you're back in the central chamber.
This bit's very important: don't go straight for the bench room. Instead, climb your way further up until you see two metal boxes with spikes on their right sides—as shown in the screenshot gallery below. Drop down and hit the lever. This'll unlock a cage, also shown in the gallery below, that you can use to get back to the bench room.
'Why do I need a shortcut, the bench is right there!' you might say. This is an entirely reasonable statement, unfortunately, Team Cherry doesn't like us very much, and has made the bench completely busted even after taking our rosaries—it's worth spending them here anyway, though, because you're probably going to bite it on the ensuing jumping puzzle.
Wall-jump up and to the left—at the very top there's a breakable wall, which'll lead to a jumping puzzle. It's pretty tough, but as a reminder, you can also diagonally strike the spikes in this room, letting you pogo (and damage boost) through some of the tougher bits.
Once you get through this gauntlet, you'll be able to smack the gears to un-gunk them, unlocking the bench. Yes, if you die you have to run back. Yes, every time. Yes, there's a boss run-back for a bench. No, I don't know what we did to deserve this. I'm sorry.