Iodine does evaporate - ask the salt water aquarium crowd. So I'm not sure that pre-mixing is the way to go.
I'm no expert, but I take mine on an empty stomach in a few ounces of water and drink it through a straw so I don't risk staining my dental bonding. Tastes bad but it really coats the stomach lining that way and gives it a better chance of being absorbed. I take my supplements at lunch with food, giving the Iodine a good 6 hours to work before adding anything else to the mix.
I have done the borax remedy for Arthritis in my knees/toes and it made a believer out of me! It makes me sad to see all these stiff people limping around using flouridated toothpaste and drinking tap (or even filtered) water. Many - I'm not saying all but who knows - can be cured with a $4 box of borax.