I designed a custom circuit and printed circuit board using a 555 timer and a 4017 decade counter to be my christmas cards for 2023.
You can see a video of me soldering one up here. You can see a video demo here.
You can find the Gerber files in this repo (the zipped file). You can find the BOM in this repo as well (bom.ods). You can also find a schematic in this repo, the .pdf file.
All smd components are 0603 size, and were soldered by hand with a soldering iron. It was tricky and not all joints are well soldered--if you have hot air gun solder paste may be a better route.