Difficulty with deploying a Flask + React app

Hi - I have a code architecture with a Flask backend (python) and a Node React frontend. The architecture of my code is as follows:

api/ (flask app)
-- api.py
-- <other flask files>
main.py
frontend/
-- package.json
-- <other react files>

For a deployment, I need to be able to:
1) start the Flask server
2) cd into the frontend directory
3) npm install && npm run build the frontend.

On my local machine, I am running the FE & BE through two different terminals.

Any guidance would be greatly appreciated!

2ac3a30b-e6a2-45ec-9a48-402e345c10b2

have a look at this https://docs.railway.app/deploy/monorepo#isolated-monorepo
tl;dr you need two services in your project, one for the frontend and one for the backend