I have a sofa in the living-room room that’s low enough, in the hallway there’s a chest of drawers that’s low and I blocked off the space under the bed partially so the bun could get in under it but not the dog. She’s rather big, which makes it easier, of course. But I don’t think my buns ever have felt the need to hide from her. She’s not interested in them, but she will eat their food if she gets the chance. If they have sth she wants she just pushes them aside with her nose and they hop away like ok, have the silly kale then.
I think it’s important for a bun to know it can hide if it wants to. I don’t think a carrier would keep a dog or a cat out, but it is nice for the bun to have a hidey-house, they do like small narrow “burrows”. An over-turned cardboard box with 2 door-holes cut out (one on either side so the bun doesn’t feel trapped) is often much appreciated. My buns love their cat-tunnels too.