How can I flirt with a guy I like at a work event?

So I really like this guy I work with and over the last year I have developed feelings for him.

Sometimes I think he’s into me too because he can be flirty at times but most of the time we are just friendly, although he does message me sometimes.

The last time we went out was our works Christmas party. He was drunk and told me he liked me and we sat together all night talking. So I’m needing some tips on how I can be more flirty with him to see if he’s actually interested or not.
How can I flirt with a guy I like at a work event?
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