i did my oven samples with a peice of tin foil folded around it at 180 degrees for 10-12 minutes.works best to chop the sample into small peices.

from mel franks' deluxe marijuana grower's guide..... "oven drying is often used by gardeners to sample their crop.small quantities of material can be quickly dried by being placed in a 150-200degree oven for about 10 minutes.it is an adequate method for obtaining dry material for testing and emergencies"