Blocks are placed around the world

I made a superflat world made of all air. I used setblock to place the initial block, but had to relog because it didn't render properly. Then, I started placing some blocks, but when I went outside the chunk, it didn't render again. I used F3 + A, and then it placed the blocks I had in that chunk that were invisible in all surrounding chunks. If those blocks are broken, The texture remains, but they can be fallen through