What???/

Carpet

What a fun idea but the only thing to slow it down would be a lower slope. Matte polyurethane would only have a marginal effect.

Add some xtra fine sand to the polyurethane.............................

Once you coat with poly it will likely be quite a bit more grippy. In fact it might be a while before it's usable.

Speed bumps!

I would love to know what you decided to try and if it was successful! we also have a wood slide going down our stairway that is unuseable unless we pile couch cushions dor safety at the bottom. I’m interested in the spray that was posted in another comment. My other thought is to line it with linoleum. In my mind that would be less slippery than painted wood.

Would love to see what yours looks like! it does have poly on it now but still quite fast. we tried a long piece of non-slip tape made for stairs down the middle which made it too slow at first but gradually wore to a point where it worked well and then to where it became ineffective. didnt look great though. Will likely use that space to create built in shelves or cabinets in the futute.

It has poly on it now which didn’t make much difference. Tried some non-slip stair tape down the middle (which did’t exactly look great) and it was too sticky at first, worked well after being worn down a bit and then ineffective after even longer. Will probably use the space for built-in shelves or cabinets sometime later on. would love to see what yours looks like!