You would just have chapters send you to that base camp chapter, and then have the base camp send you to the next chapter. You could use global flags to keep track of where the base camp should send you, if using the same map each time.
To add to what knabepicer said, in FEBuilder you can install the BaseCamp patch which disables support conversations on every other map other than the defined base camp map (map 0x39 is default I think, it can be changed).
At the end of every chapter you would have to use a global flag to mark the progress in the game so when you end the basecamp section you can make the game point back to the correct next chapter.
How can I set those global flags
How I interpretted all your advices
Was using flag condition to make base camp go a next chapter
But idk how to do that
I tried setting one up
But it sent the rom back to prologue instead
End event chapter 1 escape
I set the goto chapter Id coast
then from coast go to a tile escape with global flag trigger 7b with completion flag 7c which In that flag event I had set go to world map castle frelia
But instead. It would skip the base camp map instead and return to prologue then continue to castle frelia
With my own experience I can’t really say how to do it with the world map. Using the Tower of Valni or something easily accessible from whatever point you want to start using it may be the way to go for that since it’s accessible early on.
As for doing base camps without a world map, it depends on how you want to implement it.
The easiest method will be to make multiple base camp chapters (likely based on story) and point directly to them with the “go to next chapter without world map” command. Since it’s tied directly to the previous chapter you can point directly to the next intended chapter with ease. This, however may limit how many chapters you can make for the entire game if you plan on making a long story, and this won’t work with the basecamp patch since the patch is limiting supports to the one map.
As for a single basecamp map to use the basecamp patch, you will point to the set basecamp map like normal, but at the start of the basecamp chapter I believe you will have to use the “check whether flag is set” command in order to point to the correct chapters. To make things clean, you will want to make separate events and point to them if whatever global flag is checked. This might most easily be done by using the “if flag XX is on” template command to call the event based on the flag. The event loaded will have to be the one to start the chapter as well, and however you end the chapter (say talk to an NPC) will need to point to the next intended chapter depending on progress. You may also want to turn the flag called off in the end event since you will be using multiple global flags on the same chapter. This method will be much more complicated to set up, but will let you use the one map for multiple purposes.
If the flag was turned on in a previous event, this will check if it’s on, see in memory that it is, and run the following event. Within that event you will want to set your unit placement, any tile changes, maybe battle preps (if you want), and start the chapter.
I haven’t tested the latter option, and I may have gotten a thing or two incorrect (someone please correct me if I got things wrong, I’m not the most well versed at this), but hopefully it will be at least a start.