As we live on the west coast of Norway, on about the same latitude as Anchorage, Alaska, sundrying really isn't an option. Good thing the oven can do the trick.
Step 1: What You'll Need
You also need:
Wooden spoon or similar
Step 2: Pluck and Wash
Spread them out on a baking tray covered with baking paper.
To speed up the drying process, you can use a sharp knife to puncture the grapes. If you are drying a lot of grapes, it might not be worth it.
Step 3: Dry
You don't want to bake the grapes, just speed up the drying a bit.
This batch took about 30 hours to dry to the level I wanted. Drying times vary with different grapes and different ovens, so check on your grapes now and then to see how they are doing.
When you are happy with the consistency of you raisins, let them cool down and store them in an airtight container.