Could you explain the incident where Sai Baba instructed a Samadhi to be built for him years before his final passing?

Yes, this event occurred in 1886, thirty-two years before his final Mahasamadhi. As described in Chapter 44, Sai Baba suffered an asthma attack and told his devotees he would be drawing his life force into the crown of his head for three days. He pointed to a spot and specifically instructed Mhalasapati, saying, "Dig a Samadhi there and keep me in that place." While Baba's body became motionless with no breath or pulse, Mhalasapati guarded him vigilantly. Despite Baba's command, no one had the courage to actually dig the grave, and Baba returned to consciousness after the three-day period.