Here's one I made for my 3 year old:
This was completely made from pallets. In total I used about 3 pallets to get the different boards needed to get the look on point.
Couple of techniques I used here include:
Wood filler to seal up some of the cracks and spaces between boards. Pallet boards are rough and irregular. Of course if you want a more rustic look don't stress in filling the holes.
Hand planing boards to get smooth even surfaces. I also went back over all the surfaces with a sander to really get the smooth glass like surface. The rough, rustic look is good for some projects but when a little girl is going to be sitting on this every day, I felt it was best to make it as smooth as possible to keep the sitting experience pleasant on her little bum.
Staining with a light stain and a rag to rub in the wood. Just enough color to give it a finished look, and using the rag instead of a brush gave me the control to keep from over staining or brush marks. I really just wanted a slightly darker color than the wood is normally. This came out pretty close to what I imagined when I planned this out.
I finished it up with several thin coats of clear polyurethane. This gave it a good deal for the inevitable spill that will happen when she's having snacks and drinks on her new bench. In between coats I sanded it down with super fine sand paper that is used for automotive paint jobs.
There is a couple of ways that I could have gone with the lid piece. Hinges came to mind but I finally decided to simply make the seat portion a removable piece so when she decides to get her stuff in and out of the box she won't be bothered with holding open a lid with one hand. Instead she can take the top off, and then take her time digging inside to get the stuff out she wants.
For the back seat and the arm portions I measured then hand drew the lines where I wanted to cut the curving shapes. I used a plunge blade from an oscillating tool to carve it out, and the. Sanded rounding bevel edges to finish the look. It's slightly imperfect but I think it gives it the unique handmade look.