Liverpool risk losing Mohamed Salah, 32, Trent Alexander-Arnold, 25, and Virgil van Dijk, 33, as Bosman transfers in a year's time.
And Slot admits he does not know if the trio will extend their contracts.
"The only thing I can do is get the best out of them. If we get the best out of them and they perform really well, it's up to them if they want to sign and us if we give them a new contract," Slot told Sky Sports.
"The most important thing for all of them, whether you have an expiring contract or not, is to deliver the best possible performance and I should and will help them with my staff, to get the best out of them. So far it has been nothing but positive.
"Mo came back really strong physically, Virgil as well, Trent did the same and they delivered good performances against Ipswich - which was only the first game. My main focus is on Brentford and not on contract extensions."