That's the starting point. If you want to design boards, you can put down ESP8266 castellated modules (easy) or the ESP8266 chip itself (somewhat harder).

Because of issues with electronics supply chains, often complete boards are cheaper than you can buy the modules and chips at low quantities (things are really optimized to sell a thousand units or more). Even buying blank keycaps at low quantities was very expensive compared to finished products of printed sets of keys.