I make my own super-concentrated chicken stock, and freeze in ice cube trays. Yes, there i some loss of flavor and the risk of freezer-burn due to the increased surface area. However, just two cubes of my stock, placed into a measuring cup, and covered with enough hot water to fill it up to 1 c, will make a light stock. For more concentrated batches, I just increase the amount of cubes.
I usually thaw my stock out by the above method, but I do it when I start prepping the remaining ingredients, so that by the time I need to add the stock to the pan, it's all melted. If the cubes haven't totally melted, I don't worry about it to much.
Peace, Love, and Vegetable Rights!
Eat Meat and Save the Plants!