How to slide a non-kinematic rigidbody?

I’m studying Unity3d, coming from a 2d background, and I’m a bit confused how some things work.

I’d like to slide a non-kinematic rigidbody, i.e. “just move it forward”, like if it was hovering over the terrain. Applying a force makes a ball rotate forward, while I wanted it to slide forward without rotating, also unless that force is huge, a cube just won’t move (for the same reason).

I understand there are kinematic objects which are “easier” to “just move”, but I both think I might really need non-kinematic ones, and I think I need to understand them anyway.

edit: I did try to use some “rotation constraints”, but they just prevented the sphere from moving at all.

The rotation constraint was the right thing to do, and I thought it wasn’t working simply because I needed to increase the speed / decrease the friction.