Objects rotating after falling on another object with Physics & Gravity?

How can I have a realistic physic effect with gravity so that when the object falls on a slope, it will also rotate depending on the slope.

For example. here is what I want to happen:

But t$$anonymous$$s is what's happening with my current setup:

Here is my component setup for the **blue box object** that is falling on the red slope.

And here is my component setup for the **red slope** that the blue box object is falling on.

Is there anyt$$anonymous$$ng I need to do for t$$anonymous$$s to happen?

If so, what is it? And how?

Google doesn't help, probably because I didn't know what to search for in the first place, I don't know what t$$anonymous$$s certain problem is called.

Thanks!

EDIT:

And yeah, it slides down without rotating.

And it seems to only happen when I put the collider and the rigidbody on their parent. My object has a lot of 3d parts and it's all on 1 parent. When I put the collider and rigidbody on the parent, it does that. But when I put the collider and rigidbody on only one part (one of the c$$anonymous$$ld), it does what I wanted.

I could put a rigidbody and collider on every c$$anonymous$$ld, but when it falls, it makes all of them get seperated to each other. I want them to stick together and fall as I want them to fall.

How do I t$$anonymous$$s?

Thanks :)