This is the fastest method for dehydrating large marshmallows when none of the above equipment is available.

Place marshmallows in a single layer on a microwavable plate.
Cook at high temperature at 1-minute intervals.
Turn the marshmallows after every interval.
Repeat Steps 2 and 3 until you get the preferred texture. NOTE: Check after every interval if the marshmallows are dry enough. Do not heat for too long because the sugar is inclined to burn in this method.
Let the puffiness reduce before taking them out of the microwave. NOTE: Dehydrated marshmallows using this method shrink more than the results from other methods.
Store in an airtight container or vacuum seal for longer storage.