So looks like I did things differently and thought I’d share. I increased the Max Value on the Slider GameObject itself, got access to it from the script, and used the method Ben showed us (Time.timeSinceLevelLoad) to make it increase by a second at a time.
The startTimer is kind of redundant now, and it does make the slider look a bit ugly as it doesn’t move along smoothly, but I’m proud of it dammit!
I also made a separate Win Scene and played the win music using the Persistent Music instance from the Splash Screen, and stopped it from looping from the MusicManager script.