ANSWER:

This is authentic and it is referring to before tasleem and NOT after concluding the prayer! 

The dua should be made after completing the prayer, just before making salam. It’s time to make the prescribed dhikr after you conclude the fard prayer (after salam). 

After finishing fard salah, it’s time for making the prescribed dhikr.

The best time in salah to make dua is in your sujood and in the last tashahhud before making salam.

It’s an innovation to make dua after salah.

It says at the end of the fard prayer you should make dua but I was taught to do the dua after you finish the fard and sunnah, then do dhikr then dua// is this correct too?

There’s a hadith of At-Tirmidhi which says the acceptance of dua is after “conclusion of obligatory salah”. Is it true? (Riyad As-Salihin 1500, Book 16. Hadith 36)