How to dry up milk supply safely

I'm needing some advice on how to dry up my milk supply. I've exclusively pumped for 7 months now and I'm ready to quit. I have enough saved in my freezer to get my LO to a year. I've been pumping every 5 hours and then 5 hours and 30 minutes at night. I'm still pumping about 12 ounces or more every pump. I was going every 6 but got a clogged duct and sore out of no where. How can I dry up my supply without going cold turkey? I don't want to get mastitis or anything like that.