This was developed as I wanted to learn about removing Google Form option choices as part of exploring its capabilities for use with appointment slots. I am aware there are a number of Google add-ons that achieve this but they come with potential data protection issues when accessing your Google Account, hence an in-house approach.
The principle is simply that a user would select their desired appointment slot on the Form and then that option would be unavailable for the next user accessing the Form.
I use Google Apps Script to support staff and students in my job. I enjoy dabbling with creating tools to help with automation and I freely share my learning experiences on my blog: www.pbainbridge.co.uk