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 have pins for easy attachment but the cheapest (e.g. seeed xiao) may just have through-holes that require soldering.
• 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.