This is a Proteus tutorial to construct SR flip-flop using nand gate. Here 2 nand gates are used.
If we use the SR logic then the output in front of R is considered as Q and the output in front of S is considered as Q'.
If we use the RS logic then the output in front of S is considered as Q and the output in front of R is considered as Q'.
using Proteus, after you construct SR flip-flop, you can verify the table of SR flip-flop