Speaking of shelves - I absolutely love the "racetrack" shelves the Germans use in their tanks - gives a whole extra mezanine level!
A bit like the first photo on this page. They have a kind of narrow shelf all along the back of the tank with a little fence (mini dowels?) so they can't fall off easily. Then a sort of ramp at both ends. And they call it a racetrack. This particular one looks a bit high - some are much lower. I tried to do something similar in my cage - had a shelf at each end with a joining shelf and tube - he could get from one side of the cage to the other without touching the ground
Naturnahe Hamstergehege: Gehege - Cages - Jaulas
There's another one on here - second photo down - doesn't go all the way round. So I can see you are looking at achieving that kind of effect with the shelf unit you linked - and I too would rather buy something with legs than stick them on! But sometimes you can never quite find the right thing and sticking some dowels on a piece of wood isn't too diy-ish
Naturnahe Hamstergehege: Terrarium
I have drooled over this site before. She makes custom aquarium shelves and houses
Ebenen / Etagen / Rennbahnen - Hamster Wohnwelt
Basically though it's a piece of wood with dowels for legs and a ramp up each side.
I think they are just pieces of wood on dowel legs so the shelf sits above the substrate.