In the kernel source directory do:

    make help | less

and the various config targets are listed; to use the default configuration (for the current host architecture) do:

    make defconfig

To edit it further use one of the edit options such as menuconfig:

   make menuconfig

All of these create/operate on ./.config in the source-code 'root' directory.

This and much more is covered in

https://kernelnewbies.org/KernelBuild