You can define spawn points using WorldEdit or other plugins like EssentialsSpawn, but the combination of WorldEdit and WorldGuard offers exceptional control.
Using WorldEdit:
Equip a wooden axe.
Select two opposite corners of your build to create a selection box around it.
Type "/rg create spawn" to create a region named "spawn" within the selected area.
Customize the region's permissions using "/rg flags" to restrict building and other activities.
Managing Spawn Radius and Location:
Use "/gamerule spawnradius 0" to prevent players from spawning outside the designated spawn area.
If players are spawning in an undesirable location, utilize Essentials "/setspawn" command to set the player's spawn point to the block you're currently standing on.
This approach ensures that players respawn within the designated spawn area and cannot alter the protected region.