If you have Completed the Floor is Lava room getting in to 1-1 can be an exercise in tedium.
It is however Possible (See image for late game entrance proof)
You need to keep jumping up to the room above and get lucky with how the game unloads the conveyor tiles.
If you unload all but the spawn box and the first conveyor even with Infinity you are able to fall fast enough and just get in to the invisible block.
The first conveyor acts as a check to see if the spawn block needs to do the spawning. If it unloads the block does it's spawning as normal and the conveyor that blocks the invisible hole will spawn before you can get there.
Just keep jumping up to the room above for about a second. Throw a couple of teleports and super jumps in to the mix more or less at random on your way up or down just to keep yourself busy and slightly alter the time you are in the air for. Then just wait for the correct unloading you should get it reasonably quickly though it is RNG dependant