More in Decorating
The large pumpkin should be at least 3 times bigger than the small pumpkin.
Trace a circle in the mouth area where the small pumpkin will sit. Make the circle a bit smaller than the pumpkin (better to make the hole too small than too big.)
Use a small hand saw or knife to cut out the traced circle making sure that the hole is smaller than the widest part of the small pumpkin. Then gradually increase the size of the hole by shaving thin layers from the sides until the pumpkin fits snuggly.
Cut the top off the large pumpkin in order to gut the inside. Cut the lid slightly irregular so that it is easy to put back on. Use your hand or an ice-cream scooper to clean the inside of the large pumpkin.