When you find and break glowing blocks in Pokemon Pokopia with Rock Smash, you might find various kinds of fossils instead to use for habitats. However, actually getting Pokemon from them takes a bit of luck and effort.
How do I turn fossils into habitats in Pokemon Pokopia?
First, you need to find fossils in the world by breaking apart glowing blocks with Rock Smash. It’s not guaranteed you’ll find one, and having a Dowsing Machine with a character like Fidough can help your odds. When you do get pieces, you’ll potentially find 1×1 like a Jaw Fossil (Tyrunt) or Armor Fossil (Shieldon). Multipart fossils that consist of three parts, like the Wing Fossils (Aerodactyl) or Despot Fossils (Tyrantrum), require a 2×6. To construct the habitats for each, you need a single Exhibition Stand for a 1×1 one or six for the larger creatures.

What I recommend is waiting to assemble habitats with fossils in Pokemon Pokopia until Rocky Ridges. That’s because breaking the rocks to the right of the Pokemon Center in the space where you can find DJ Rotom and following the track will lead you right to the ruins of a museum. There are a number of Exhibition Stands already set up, so you don’t need to craft your own with lumber and stones. Not to mention it feels neat to have all the fossil Pokemon in a museum together. However, you can start finding Shield and Armor Fossils, as well as the Exhibition Stand recipe, as soon as Withered Wasteland, so you could get a head start sooner.
If you get doubles of fossils, keep them! If you trade them at a Pokemon Center with a character working there, they tend to be worth about 1,000 points each and can be a great way to get more valuable items.
Pokemon Pokopia is available for the Switch 2.