How would I make it so you can still destroy a block, but the player (and other mobs) can't collide with it?

I am trying to make custom decorations for my mod. When I was making some, however, I set the bounding box size to the size of the model, except now you can collide with it. Since it is tiny (ex. flowers), I do not want the player to collide with them, but I want the player to be able to destroy them. I tried setting the box size to 0x0, except that prevents you from destroying them. So, how would I go through doing this? Do I need to use custom code?