I needed to reset the footings for a water butt and instead of using a single block or slap of concrete, I used some old bricks and slab. Leaving a gap will give a home for newts, toads, insects etc.
I am sure if you look around your garden or any accessible land you may be able to create just a small spot that insects and birds will benefit from.
Add bush/hedge cuttings to a rough corner instead of filling your bin will make a home for some wildlife. The more rough corners with decaying wood the better.
Another simple thing you can do if you have any trailing plants: I simply made the ivy into a knot, added extra twigs and secured a nesting area for birds.
Ivy is also a great source of late nectar for bees and other insects. If it’s not a real nuisance, please leave it.
Old Christmas Tree
Inspired by Marcus’s post, I thought I would use my old tree this year and some hedge cuttings interwoven to make a rough corner. Adding some old logs in the bottom will also help wildlife.