Remember that any raise from your side at an early position will lead to an all-in on the opponent's side. Even at the first level of the game.
And let you have the hand AK and J-J and above, remember that there will always be at least a couple of players against you.
Even when you have AK in your hand, and the flop is A-T-9-5-3, it's better to call.
Of course, sometimes you will see 9-5 or 4-2 in the opponent, but most often there will be A-Q, A-J, K-K, Q-Q, J-J or even the second pair. Top pair and top kicker is usually the best hand in freerolls.
If you find a pair of jacks or a higher hand, then you do not have to slowplay. Do not try to set a trap, do not build a poker genius.
Just push all-in. You will be called by many weaker hands (sometimes they also win), but more often than not you will simply double / triple your stack even at the earliest stage.
And when you get to the late stage of the freeroll, then you can go back to the good old ABC-poker, because all the "casual passengers" will already come off the race.