As the level of production of the original "Sanders Sides" series had risen to a level where each episode took literal months to be made and released, this spin-off series was created with the intention of featuring more Sanders Sides universe content in-between the main episodes, also to explore alternate ideas that didn't fit in in the original narrative or didn't give enough for a full length Sanders Sides episode.
Each episode of "Sanders Asides" is always set after the last episode of "Sanders Sides" that was aired before it (or Asides if there's no Sanders Sides episode between two consecutive Asides episodes).
The original idea of the Sanders Asides series was to provide lighter and shorter episodes that wouldn't advance the main plot of Sanders Sides. However, this quickly evolved into equally long and plot-heavy episodes where the only difference with the main Sanders Sides series is, in words of Thomas Sanders, that they don't discuss mental health topics and focus entirely on the characters and the plot. It had already been established that the Asides episodes were canon, but this new focus made them also essential to the viewing of Sanders Sides.