It's a must! Let's be real about it... If I'm uncomfortable or hurt myself I will spend less time doing it, if any at all. This way... No excuses!!
But seriously, I have RA... so bending for extended periods of time isn't an option. And if I was to get down on the ground... I'd be there waiting for someone to come home and get me up. The tall bed at the back was our first attempt. Way too tall... to fill. But perfect for absolutely no bend. So we cut down the rest, filled them all with straw bales and cardboard. But that one is my favorite. All my pollinators are going in that one.
So keep this in mind then... Once you fill the rest of the box with your chosen dirt.... The corners will sink. Each of our boxes holds 2 sm square straw bales. Then I laid cardboard over the straw. Then I filled the rest w/ dirt. I assume the weight of the dirt pushed the cardboard down in the corners. So... Maybe initially, just add some extra dirt to the corners. I got most of them planted, and then went out after the rain and each box had at least 1 corner sunken.
Not a huge deal, but at first I thought I had a critter! 
