Hello @gauravjain1
Kindly check the official Devdocs where we have demonstrated regarding Package Development & Shipping Method Devlopement
Package Development : https://devdocs.bagisto.com/2.3/packages/
Shipping Method Devlopement: https://devdocs.bagisto.com/2.3/advanced/create-shipping-method.html#introduction
Warm Regards
Team Bagisto