Cover the cups with plastic wrap then refrigerate until set. (jellibeanjournals.com)
You can then leave out at room temperature for 30 - 50 minutes until solid or just refrigerate until set, about 10 - 15 minutes. (greensofthestoneage.com)
Sprinkle the top with flaky sea salt, then refrigerate until set, 1 hour. (tastingtable.com)