Cypher might be the one to answer this as she's had many dwarf hamsters and various houses. I think they like labyrinth houses like the ones by Getzoo and Rodipet. But I have a Roborovski and he ignores all the houses I put in and nests under a shelf and burrows down. Larger dwarf hamsters do seem to prefer a house. I have a labyrinth house for a Syrian and it makes a good additional platform. The litter tray goes inside it. You can also stick wood dowel legs on the house so it sits on top of the substrate and they can burrow under it without it falling on them. Or have it on very little substrate with the substrate piled around it so it's like a subterranean house (you just channel out some substrate near the door area). They can get squashed if trying to tunnel under a larger house, so it's either virtually on the base with hardly any substrate, or legs and sat on top of the substrate - for safety. Another alternative is a shoe box house.
I think Cypher had this one for a dwarf hamster
https://www.getzoo.de/getzoo-wohnlabyrinth-xl-xena.html
I have the larger, Syrian version, of this one - the rooms are good. Our hamster nests in the front left and toilets in the middle back so the litter tray goes in there.
The terracotta dish is good (I use it as a food bowl) because you can lift it out and the hole underneath is big enough to take the potty out without having to take the whole roof off.
https://www.rodipet.de/shop/haeuser/...erracotta.html
I think they tend to use labyrinth houses if there is one in the cage, because it's dark inside and a bit like being under a shelf.
Rodipet actually sell wood legs to stick on the houses!
https://www.rodipet.de/shop/haeuser/...nci-serie.html