What is the most climatically stable and geographically sound way to create a California sized Mediterranean style sea?

Greetings, I'm working on a fantasy project with friends and quickly hit a roadblock. I want to create a California sea. Climate wise, that's the Med or Jomon Japan, but want to create a sea that's about the same size as the US state of California or the country of Turkey. I'd like to include islands, similar to Crete, Sardinia, Sicily, and Corsica. How would I create such a sea to have the islands in climatically stable sea. I've searched the term "Mediterranean sea" and California and find mostly geographic information on the western coast of California being a "California Mediterranean climate zone," but not how to create a sea that is similar to the Mediterranean sea itself. I've also looked up "Sea of California" and that doesn't create an island that is part of the sea. Thank you.