Instructions
Catch or trade for a female Snorlax and let it hold the Full Incense. Leave Snorlax at the Day Care Center in Solaceon Town with either a Ditto or a compatible male Pokemon such as Torterra or Garchomp.
Ride the Bicycle back and forth between Route 209 and Route 210 until the Day Care Lady's husband takes a step forward. Talk to him in order to receive an Egg.
Ride the Bicycle back and forth between the routes until a dialogue box pops up with the word "Oh." Confirm the message. The egg will now hatch into a Munchlax.