FTP is driven by VO2 max, and VLaMax. Do workouts to boost VO2 max, and reduce VLaMax.

A combination of long endurance rides and VO2max/high threshold workouts boost VO2max.

And sweet spot rides reduce VLaMax.

Which workouts will be most effective to boost your FTP depends on your physiological profile and where you are currently on these metrics. Eg if VLaMax is high, and VO2max is high, focus on reducing VLaMax via sweet spot.

There’s a lot more insight and detail in the following post.