Read about the concept of Viparita Raja yog here
Phaladeepika describes about Sarala yog as below.
Definition
“If the lord of the 8th house is posited in the 6th, 8th or 12th house it forms Sarala Yog.”
Description
“The person born in this yog will enjoy longevity, be resolute, fearless, prosperous, respected and endowed with learning, children and wealth. He will be successful in all his enterprise, overcome his foes, be pure of mind and widely celebrated.”
Notes
The underlying concept of Viparita Raja Yog given in Uttara Kalamrita (Refer here) aligns with this Yog of Phaladeepika.
Where basics, of Dussthana lord placed in other (or same) Dussthana house gives favourable effects and end results, is kept under light.
Harsa Yog - Viparita Raja yog by 6th house and its lord
Vimala Yog - Viparita Raja yog by 12th house and its lord