This is a rough outline of how you could start/stop FullStory based on user consent.

fsOptIn.js

// For example purposes only

// Set up all of your variables here
// buttons, defaults, etc.

function loadFullStory(){
  // Put Your FullStory Script Here
}

// Determine if FS should start recording based on an input value from a 🍪 bar or modal, really any user input
function recordingCheck(optInVal){
  
  // Ex. Getting a cookie value
  var status = getCookie(optInVal)
  
  if(status === "accepted"){
    
    // Make sure FullStory is available
    if(typeof FS === 'function'){
        FS.restart()
    }else{
      // If FullStory is not available, load it. This will auto start a new session.
        loadFullStory()
    }
    
  }else if(status === 'declined'){

    // Shutdown FullStory only if it is running
    if(typeof FS === 'function'){
      FS.shutdown()
    }
  }else{
    // Set default acceptance level of declined
    setCookie('fs-consent-level', 'declined')
  }
}

// Ex. functions to set cookie values and run the recording check
function declineCookies(cname) {
  setCookie(cname, 'declined');
  recordingCheck(cname);
}

function acceptCookies(cname) {
  setCookie(cname, 'accepted');
  recordingCheck(cname);
}

// Event listners for buttons
declineCookiesBtn.addEventListener("click", function () {
  declineCookies(cookieName)
})

acceptCookiesBtn.addEventListener("click", function () {
  acceptCookies(cookieName)
})

// Intial check
recordingCheck(cookieName);