Mogg Flunkies can't attack or block alone.
3/14/2017 Mogg Flunkies can be declared as an attacker only if another creature is declared as an attacker at the same time. Similarly, Mogg Flunkies can be declared as a blocker only if another creature is declared as a blocker at the same time.
3/14/2017 Two or more Mogg Flunkies can attack or block together.
3/14/2017 Although Mogg Flunkies can’t attack alone, other attacking creature(s) don’t have to attack the same player or planeswalker. For example, Mogg Flunkies could attack an opponent and another creature could attack a planeswalker that opponent controls.
3/14/2017 If an effect says that Mogg Flunkies attacks or blocks if able and you control another creature able to attack or block, you must attack or block with Mogg Flunkies and that creature.
3/14/2017 In a Two-Headed Giant game (or in another format using the shared team turns option), Mogg Flunkies can attack or block with a creature controlled by your teammate, even if no other creatures you control are attacking or blocking. In any other multiplayer variant, it ignores each other player’s blocking creatures.