That's not a concern, Melissa. I have the densest, thickest cork I have ever seen. They are in big slabs, so I would cut a 1'x1' piece easily. A standard slab of cork would be 1 1/2"-2" thick and a 1'x1' slab would weight 1-2 lbs. I have some that are 3"-4" thick and weigh 3-4 lbs. for that 1'x1' slab. They would never tip over, not with a bonsai plant.