@mardh take a harder look at this link:
https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html#configuration-layers-path
specifically
To include libraries in a layer, place them in one of the folders supported by your runtime.
Node.js – nodejs/node_modules, nodejs/node8/node_modules (NODE_PATH)
Example AWS X-Ray SDK for Node.js
xray-sdk.zip
└ nodejs/node_modules/aws-xray-sdk