I have a design spec that looks like this:
As you can see, the container can either have a row of 2 columns or a row of 1 column. The row with 2 columns also has a space between.
Using flex, how can I make this possible? The columns comprise of simple hardcoded <View>s.

You should probably use
inine-flexhere if you don't want to use grid. Maybe this solution will help you: Sandbox