How to configure a custom toolchain module from the project ?

[mtribiere]

I'm have a custom toolchain in a module called build_tools_reloaded. So far it works and I can make a toolchain like so:
build_tools_reloaded/toolchain/BUILD

my_toolchain(
        name = "my_windows",
        cc_flags =  [... ],
        cc_includes = [...],  
        link_flags = [...],
        compiler_path = "gcc",
        archiver_path = "ar",
        linker_path = "ld",
        stripper_path = "objcopy"
    )

toolchain(
        name = "my_windows_toolchain",
        exec_compatible_with = [
            "@platforms//os:windows",
            "@platforms//cpu:x86_64",
        ],
        target_compatible_with = [
            "@platforms//os:linux",
            "@platforms//cpu:ppc",
        ],
        toolchain = ":my_windows",
        toolchain_type = ":toolchain_type",
    )

However I'd like to be able to configure this toolchain (the flags, includes,...) from the project that has this module as dependency. I'm thinking somethinbg like :
myProject/BUILD:

[...]
init_my_toolchain(user_flags = [...])
register_my_toolchain()
[...]

I'm not sure if this is the right approach thought, and how I could implement that.
Thanks for your help