Please read through the links I gave you and try to build something from that. You can't "just" use a random buffer of unknown lifetime with Erlang. You have to create a resource, which is essentially an opaque handle in Erlang to track a foreign object, and then attach a resource binary to it. To make this safe, the lifetime of the referenced slice must be less or equal the lifetime of the resource. The tests for this are here:
https://github.com/rusterlium/rustler/blob/f1aaa3b6d886f0685489c6ffaffb2142d9f7e861/rustler_tests/native/rustler_test/src/test_resource.rs#