Coarsely grind bud to about hemp seed size pieces. I recommend a food processor or coffee grinder, though for small batches a hand grinder will work fine.
Add desired amount of your preferred cooking oil (remember potency is variable and ratios for medicine vary by patient) and combine in sauce pot equipped with a candy/oil thermometer. Turn on burner to med-hi heat.
Stir constantly. As you can see the buds will turn a golden color while cooking. Using buds will prevent the strong grassy flavor that comes from extractions made with trim or shake.
Continue stirring constantly until you reach 300, which is below the temperature at which most cannabinoids burn. Once you reach 300 immediately remove from the burner. This will prevent bitterness by not burning your buds, while getting all the medicine possible by heating to the proper temperature.
Strain oil through a mesh kitchen strainer. You can use a ladle to press the plant matter to ensure you've removed all your extracted oil. Measure your extraction and replace oil lost during process to return to your original amount of oil for easier dosing.
Pour completed oil into a mason jar and use as desired. Voila!
NOTE: The photographed extracted oil is very dark because I use hemp cooking oil for infusion and it starts very dark, if you use canola, vegetable, or olive you will have a much lighter colored extract.