It is possible that she could have been bred before you got her. I'd question whoever you got her from.
There a good chance that she'll have the other eggs passed before you even read this. Toss out the slugs. Different breeders use different incubating mediums. I use spagnum. Others use vermiculate or perlite. If there are any nice, round, white, fertile looking eggs you'll want to set them up in a container with a fairly damp medium. Try to keep the humidity in the low 80% or so range and open the container for a bit daily. You'll want to keep the egg box in a fairly warm place with temps in the low 80F range or so. Don't freak out if you see a little bit of variation in temps. With luck, the eggs will hatch about 65-70 days or so after being layed.
If there is not enough ventilation, the eggs will mold and die. If they get too dry, they'll shrivel up on you.
It is completely natural for the snake to go off feed 3 weeks before laying so no probs there but I'll bet that it sure was a surprise!!!
Just make sure the female has plenty of water and is well hydrated after she drops the eggs. I like to feed a small meal within a day or so after laying is done before she starts the post lay shed. A couple of days after laying she'll go into a post lay shed and probably won't eat at this time.
Hopefully others can add to this or hit on anything I missed.
Best of luck