The two clubs have reached a compensation fee for the Dutchman.
"Nothing has been officially confirmed yet," Slot said on Friday ahead of facing PEC Zwolle this weekend.
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"I'm sitting here with the Feyenoord emblem on my chest, so in principle the intention is that it's all about Feyenoord.
"I have said before that I am confident that it will be done. I don't know when that will be. But I expect an agreement will be reached."