You can build an edge triggered flip flop from just NAND gates. Real world gates have delay, which means that you can generate the enable signal by using a NAN

You can build an edge triggered flip flop from just NAND gates. Real world gates have delay, which means that you can generate the enable signal by using a NAND gate to invert the clock and generate a pulse on the edge of the clock by ANDing that with the clock.