How do I let this guy know I think he’s cute?

I work with this guy and we’re in two different departments so I see him in passing but I want to let him know I think he’s cute. I found his Instagram so we followed each other he liked an old photo of mine so I did the same. Today I saw him in passing at work so I said Hi to him he said hi back but it was with a quick look then he kept walking. How do I kinda put the ball in his court to see what he does.
How do I let this guy know I think he’s cute?
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