First I made the legs and screwed the sides onto them. I reused the blocks from the pallets as well to give the legs some strength.
I then selected planks of the same thickness to use for the top. I screwed them on using four screws for each plank - two at each end. Rather than drilling pilot holes I gently tapped the screw into the wood with a hammer before screwing it in the rest of the way. I also added at this stage a plank at each end between the legs for added support.