God is supremely free.
God is a slave.

God controls all. No one controls God. God is free to do what he wants. God is free not to do what he doesn't want. God is free to do inverted actions meaning, for example, God can see with eyes if he wants, God may not see with his eyes if he does not want, God can see without eyes (inverted action) or God can talk with eyes, God can hold with eyes, God can touch with eyes, God can breath with eyes, God can perform all the actions of all senses with one sense.

This is 'Alukik Karani' or 'Unthinkable actions of God. Thus God is free to nothing, anything, everything that too in unthinkable ways. Therefore God is supremely free.

But God is slave to his devotees. He says, 'It is said that I am free but really I am at the will of my devotee.'

God is slave to Saints because Saint has one power - 'spiritual love' which bind God in the bond which God cannot break and hence behaves as per wishes of his devotees.

Thus God is supremely free
Yet he is slave to his devotees.