Create experiment from custom js/html

Hi there,
I’d like to use pavlovia to host and store online experiments. I have previously run custom javascript applications (not using lab.js, psychopy, or other) and would like to adapt one of those experiments to run via pavlovia. I had a look at the labjs-pavlovia-3.2.5.js and jspsych-pavlovia-3.0.0.js files… would the easiest way be to write my own code to open and close sessions? What are the requirements for the config.json file to contain?
Thank you!