Custom Portal Locations

Is there a way to create custom locations for portals to spawn at? 

Portal locations are dynamic. With auto-spawn, they are generated automatically, and when buying an event, the portal spawns near the player who purchased it.

What does this mean exactly?

""Radius Contruction Block on Dungeon Portal"

5 hours ago, Martian said:

Portal locations are dynamic. With auto-spawn, they are generated automatically, and when buying an event, the portal spawns near the player who purchased it.

 

I know they are random, that's fine, but I want to be able to set my own locations and be able to have portals on foundations. 

These Random spawns are still too far away. There's no option to even make them closer.