If you are looking for a great and simple program for building posterior (as well as overall) strength. Check out Pavel Tsatsouline "Kettlebell Simple & Sinister" program [1]. All you need is a couple of kettlebells and 5*30 min a week. It's very much a minimal effort, maximum effect program.

[1] https://www.amazon.co.uk/gp/product/B07ZQKWMKR