Here's a copy of a post I made to the gardening thread. I'm posting it here, too, and adding a little bit more info you related to the pallet wood build specs...
I saw on YouTube that fresh cut grass clippings, about 1-2 inches thick, make an excellent top mulch for the gardens. So, I mulched up a couple raised beds the other day with grass clippings.
Eggplants and peppers in this pallet wood raised bed I made last year...
Tomato plants here in my newly designed pallet wood raised bed I built this year...
I like the looks of the green grass clippings. Another option I was considering was using unfinished compost from the chicken run. Anybody got some thoughts or suggestions on top mulch options that work for them? Thanks.
Additional Info for the pallet wood build specs: The top photo pallet wood raised bed design from last year used pocket hole screws to hold the frames to the 4X4 posts. Pocket hole screws are not extremely expensive, but I figured I had about ~$5.00 in pocket hole screws in that build.
The lower picture of the newly designed pallet wood raised bed did not require any pocket hole screws, just basic wood screws. I estimated that I spent maybe ~65 cents on this new build. Also, this new design is much easier and faster to build because it does not require any pocket hole drilling and screwing. Using pocket hole screws on last year's design takes more time than this new design using basic wood screws straight on into the wood. Also, I really wanted to use up some of those 2X4's with the forklift cutouts in a pallet project. I think the cutouts, in the new raised beds, look pretty good.
I just thought photos having both pallet wood designs, filled with plants and top mulched, give a nice comparison of the designs that I have been building. Both pallet wood raised beds are 4X4 feet. Our big box stores sell kits for these type of raised beds but they cost about $150.00. And, I don't think those kits are as strong as these pallet wood raised beds I built for a fraction of the price of those store kits.
For comparison, here is a
kit from Menards of a 2X4 foot raised bed - costs $210.00

It would take 2 of those 2X4 foot kits and over $400 to make one equivalent 4X4 pallet wood raised bed that I built for less than $1.00. Makes me feel pretty good about building my own garden beds out of pallet wood.