EarthBoxes on sale Dec 14 and 15, 2019
 

According to an email:

Everything on site (with a few exceptions) is 20 % off.
Also, most importantly, Free Shipping. But you must spend over $79 AFTER all the discount have been taken.

End 15th at 11:59 EST

So, if I have this right, you would need to buy 3 EarthBoxes at $32.95 each to get 20% off and the free shipping. (That would be 8 cents over $79.)

Of course you can mix and match whatever you want.
Just be mindful of the restrictions.