Comment by t-3

Most of the native bees/wasps/flies that are important for pollination are solitary, but you can still help them with nesting areas.

Mason bees can be relatively easy: drill some small holes in a post and let it be. You can also get way more complicated with it.

https://colinpurrington.com/2019/05/guide-to-diy-mason-bee-h...

Bumblebee make nests for breeding, you can sometimes find nests in birdhouses or in gaps of buildings, but they apparently usually go for old mouse burrows. I've seen guides similar to the following, but covering a nest of dried grass with a clay pot, with a buried hose connecting the inside of the nest to the outside.

https://www.ars.usda.gov/ARSUserFiles/20800500/BumbleBeeRear...

Planting native flowers and shrubs can also provide habitat for many insects.