What is the easiest way to transfer a file from Windows laptop to Samsung phone without USB cable?

Use an App that transfers the file using available Wifi bandwidth.

For that, use ShareIt. It transfers files over Wifi.

You could download ShareIt for Windows from their official website and run both of them (on smartphone as well as on PC) and transfer the file.

Hey, The safest method is to upload your files on Google drive, and then you can access it from anywhere.

If your files are big, then you can use file sharing apps like Shareit, Xender.

These apps are available for both Windows and Android.