Question: how is sujud qabli performed?
Answer: Qabli (omitting from the prayer out of forgetfulness) Before making the tasleem (i.e. saying as-Salaam 'Alaikum on both sides) the person must say the takbir (i.e. Allāhu Akbar) while sitting and then make two prostrations as per normal sujud. Then the tasleem is made.