Providing flowers is not the only way to improve habitat for bees. Many species have relatively specific nesting requirements that can easily be supplemented. Bee hotels are becoming a popular way to attract and support cavity nesting pollinators, which include numerous bee genera, primarily in the family Megachildae. If the hotels become occupied, they then attract additional species including cleptoparasites and scavengers, providing great photography opportunities. Caution should be taken to avoid the hotel becoming a breeding ground for invasive parasites and fungus.
Simple hotel examples
A great guide to building and maintaining bee hotels can be found here.
If you create a bee hotel, or find an active one, iNaturalist observations can be added to this project.