Now that I'm not on my phone, I am going to post this. Here's a staircase from my map, koth_anthem.
Using an arch to do this is easy. I made a brush something like 512 wide, 512 long, and I think 8 units high. I made arch width the width I wanted my stairs (128). Then I put 16 into the Add Height field. This gave me a set of circular steps. The only math involved is figuring out how many steps you want versus how high they should be, and it sometimes requires a bit of trial and error. My stairs here are actually a 32 piece arch but in only 90 degrees, met up with a regular, secondary arch I made later (the platform) so it's a lot more complex than most.
To clip it, I did basically the same thing but didn't put anything in the Add Height field. To make it line up with the steps smoothly, I had to cut each section of the arch into triangles. The way to do it is to start at the outside edge of the bottom and work inward. You will probably have to be on the 1u grid to do this correctly.
When you've got it all cut into triangles, select all but the bottom two vertices as seen in the top down viewport, like this:
Very, very carefully move all the points up the height of one step. You should be able to use the tops of the bottom-most pieces as horizontal guides. Be very careful not to slide things over because it's incredibly easy to make an invalid solid at this point.
Keep working at it and you end up with this:
It's really just time consuming, not hard or tricky. Carving
will cause you so many issues that there is no reason to not just take your time and do it correctly.
I used the same method for the trim as I did for the clipping. It was just more annoying.