The Me109 slats, at least on the "Gustav" (Me109G), had no springs. My basic understanding is that the slats extended when the stagnation point moved below their leading edge as AoA increased. In the Me109, if you had any sideslip present then one slat would extend before the other. However, no roll-off occurred which would tend to prove the above mentioned point that for a given AoA the coefficient of lift (Cl) is the same with slats in or out (but read on!). Another way of looking at what they do is that they extend the Cl vs AoA curve to a higher value but do not displace the curve left or right (whereas flaps displace the Cl vs AoA curve to the left).
I have read reports that the Me109E did drop a wing as the slats extended but that was quite a different wing to the "Gustav". Also, I seem to remember that the A4 Skyhawk had such slats, and that these could deploy asymmetrically giving a roll-off to the extent that the Blue Angels welded them fixed! Any USN A4 drivers confirm this?