When we start learning a new processor we often start with a very simple circuit. We often assemble that first circuit on a breadboard, and face the challenge of debugging our first program for an unknown processor, using a new IDE, a new emulator or programmer, and an untested HW.
Sometimes we are lucky to have an evaluation board from the manufacturer, but these evaluation boards often focus on the advanced features of the microcontroller, and they are far from ideal for our first baby steps.
I designed this PCB long after I have learned STM8L programming the hard way. I hope it will make your life easier.