Where to put my basking dock in tank for red ear slider turtle?

I have a 30L x 12W x 12H 29 gallon tank and i was wondering wheres is the best spot to put his turtle dock i bought him right now i have it in the middle of the tank but i was wondering if i should put it in the corner because the basking light would heat up the rock a bit more when its on the side because i have it clamped onto my curtain rod. where do you guys have your basking areas at?