I don’t like the “to do in advance” translation at all, because it’s awkward. Instead I like to translate it as “to do something and leave it like that (for some reason)”. So in this sentence it would be translated literally as “Would you take the blowfish out of the oven and leave it like that?”.
Some other examples:
“窓を開けておきました” - I opened the window (and left it like that)
“冷蔵庫に食べ物を入れておいたよ” - I put the food in the fridge (and left it there) [for you]
So the point is always to specify that the object of the action was left in the state you put it in for some reason.