To mark a snippet as favorite, simply tap the star on the bottom left corner of the second. Don't worry, we automatically favorite the video you add in a day.
So why select a favorite?
We know not everyone is going to want to mash together all their seconds. So we added the option of picking "Favorites Only" or "All Snippets" in the mashing screen. When you have "Favorites Only" selected, we'll mash a video of the seconds you've favorited (starred).
FYI: You can always go back and fave or unfave the second of a day.