I have flat feet

You can qualify for IDF service also with a low health profile.

This might lower your profile, but would certainly not disqualify you from serving in the IDF.

The degree to which it hampers your activity and your attitude to the problem play a significant role here. If it does not significantly hamper your activity and you express that when questioned, it might not lower your profile a great deal or even at all.

You might want to consult a physiotherapist before enlisting, have insoles made for your boots, and consider an exercise regimen to strengthen your legs.

If you show motivation, and you truly believe that your feet won't bother you enough to interfere during your service, you should be all set --- most people with flat feet get an 82 -97.

And lets say you have serious flat feet problems and a low profile, you'll go to shiryon (tanks) and become a tank fighter, or maybe tothanim (artillery).