What is the safest way to get a base for a tan?

There is no safe tan. There is no safe way to get a base tan or any tan. A tan = damage to your skin. Tanning booths are just as damaging as the sun. "fake" tans with self- tanner or spray tans are probably safer but don't protect you from a sunburn. The best idea is to where lots of sunscreen, a big hat and sit in the shade when outdoors. Your skin will thank you and you will thank me when you have less wrinkles.
Oxymoron... That is, there is no such thing as a safe tan. Tan=sun damage. Sun damage leads to aging (wrinkles, discolorations, etc0and increases risk of skin cancer. The only "safe" tan is a fake tan.