Does that mean it’s possible to build radio receivers by ordering the parts and assembling them yourself, Ikea style? If yes, then how can I go about doing this?

Depends on what you mean by "build radio receivers"

• The LoRa boards that work with Meshcore/Meshtastic are so cheap and plentiful that folks usually just buy the board and assemble it in the case of their choice with battery, antenna, etc, of their choosing. {Most boards available at retail have factory-installed connectors for easy attachment but in some cases one might need to solder.}
• you might mean "build a LoRa board from components" but a person who could do that probably wouldn't be asking the question <- not trying to be a jerk, can't think of another way to put it pre-coffee.

{edited to reword section about pins}