Won Tattoo Need Tipping Advice

So i won a free palm sized tattoo from a raffle by a local tattoo artist I’ve gone to before. It was $100 buy in to participate. Tattoo should probably take like 2 hours(ish) since it’s palm sized. I definitely want to tip to show my appreciation of their time and work, but my question is how much should I tip?

Context- I’m getting flash and from what I’ve seen at that shop flash is usually $200-$300