Dyche penned terms to 2022 yesterday.
Garlick told Clarets Player HD: “We've had a great season so far and with that always comes speculation about clubs being interested in your manager.
“Hopefully, again what we're doing today means we can plan for the future and there's a big 'keep-off' sign there with a four-and-a-half-year contract."
Dyche, who had previously been on a rolling 12-month contract, has led the Clarets to two promotions to the Premier League since his appointment in October, 2012.
And Burnley's current position of eighth in the top flight is their highest since 1975 as the club continues to build on and off the pitch.
“Hopefully it's the signing of the window, or certainly the extension of the window," added Mr Garlick.
“I think it's a deal that suits the manager, it suits me as the chairman and the board and, most importantly, suits the club.
“One thing we have always wanted is a stable club, and Sean signing the contract today means we can build and plan for the future.
“I think if you can do that, you've got a far better chance of success. And – by the way – he has earned it."