One rakkah is acceptable. It is the minimal reward  you would get for it.

As for the ways of praying witr:

https://m.youtube.com/watch?v=KNBFy3vs9MM

I sometimes used to pray only 1 rakat in witr prayer but after some research work and discussion with a friend I thought I shouldn’t and I started to pray 3 rakats with one jalsa at the end. My question is can I pray only 1 rakat in witr? And make it habit? Is it acceptable? And I mostly pray 3 rakats without sitting in second and very rarely I pray 2+1 I.e Salam at 2nd rakat

Prayer | March 27, 2017 5:26 pm
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What is the correct way to do tasleem behind the imam. Some people do it with the imam simultaneously, some after the imam has finished tasleem, and some after the imam has done one side he does that side and so on.