Here are a couple of sites that may help:
https://www.gardeningknowhow.com/ornamental/trees/sago-palm/repotting-sago-palm-trees.htm Click on the 'next' section to learn much more about Sago palms.
Twice as deep as the root system
do not bury any of the trunk that has previously been above ground or you'll cause it to get rot,bugs,disease. While most palmsdon't have invasive roots, the root systems extend laterally(wide) as far as the crown(outer edges) of leaves, enabling them to harvest water from a wide area of soil. Outside? the base needs put in hole that will accomondate the entire root ball and then add 3-4 "s of space around so no roots are broken off at planting time or digging up to transplant.Sagos and other palms do not have woody roots like most of our woody ornamentals but they are massive and will continue to grow in length as long as the palm is alive. It might be best if you avoid planting near the septic tank or well areas. The roots of palm trees reflect the fact that they are monocots and are related to grasses and onions ... In a pot? only 4"s bigger than first pot wider pots are better than deeper.
I found a video that tells how to plant a Sago Palm...