Grammar
Style guide 
complement and compliment
complement
Complement means to complete, go with (e.g. pepper and salt complement each other)
compliment
Compliment means to praise. It's also a formal formal expression of civility or respect (e.g. compliments of the season).
So do you say complement/s slip or compliment/s slip?
Both compliment/s and complement/s slips exist in Google, but I think, using the second meaning of compliment, I'll choose compliments slip in future.
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