IF USING NEXTJS and TYPESCRIPT

For me, the issue was because, I had initially installed react-slick as a dependency rather than as a dev dependency.

I did the following -

npm uninstall react-slick @types/react-slick

npm install react-slick @types/react-slick

npm install --save react-slick @types/react-slick

Now, although its redundant having react-slick in both as dependency and dev dependency, however, thats what worked for me.

Good luck!