How can I deal with monster spawns in Sokoban?

A few times recently in Sokoban, I've been having issues with inconvenient monster spawns that end up blocking my boulders. I most frequently run into this trouble when I'm nearing the completion of a level, when the level's long "pit corridor" is almost entirely filled in. Although I've verified the hallway as being fully clear of obstacles ahead of time, by the time I walk back to my boulder and push it all the way through the passageway, occasionally a monster has suddenly appeared in the hallway in front of the remaining pit(s) and I get stuck.

The only thing that I can figure is happening is that a monster is spawning in the passage after I check it, but before I'm able to get the boulder to the pit (with no real opportunities to re-check the corridor as I move the boulder due to the structure of the level). I can always destroy the boulder and use/create another, but I'd obviously like to avoid the Luck penalties if possible.

Is there any good way to mitigate the odds of this happening, and/or fixing the problem when it does? Methods that would be reasonably accessible to an early-game character (and, ideally, without assessing Luck penalties) would be preferable.

Solution 1:

Ranged attacks, with the exception of force bolt/wand of striking (which destroy the boulder in the process), pass over boulders just fine and let you kill whatever is on the other side.

If you don't have any ranged weapons or suitable attack wands of spells, in the worst case you can leave sokoban, smash a boulder, and get rocks to throw.

If you have a wand of teleportation, you can also teleport the boulder (and, in the long hallway, probably the monster behind it as well) with no luck penalty. Note that the boulder way very well end up in an inconvenient place.

Solution 2:

If no ranged attacks available, you can also squeeze past the boulder (Walk into it while carrying almost nothing). Drop all your gear (take off armor) and walk into it. Usually I'm able to bring a weapon that way. But beware: this inflicts a luck penalty.