Video production moved pretty fast at Flocabulary. A lot of thought went into which videos to give extra attention to, and which to streamline. One of the most effective time- and cost-saving strategies that I developed during my tenure as Director of Animation was to periodically hire an illustrator to create a big batch of assets to be reused across a series of videos. It was loosely called the Math Template since it was primarily used in math videos, but we worked it into ELA (especially grammar) videos as well. The template consisted of a handful of characters with different styles and skin tones, funky accessories and gizmos for them to fly around on, plus a myriad of backgrounds with center-screen open space to present the meat of the lesson content, whether it be equations or sample sentences. This template strategy saved us tons of money across dozens of videos, while maintaining a sleek artistic look, thanks to our network of amazing freelance illustrators. 
I art directed different templates with different illustrators. Here are a few examples from the version illustrated by Jeannie Phan. 
Multiplying Decimals

Directed by Drew Roberts
Illustrated by Jeannie Phan

Full credits at flocabulary.com

Dividing Decimals

Directed by Drew Roberts
Illustrated by Jeannie Phan

Full credits at flocabulary.com

Stills from the Template