In this paper, we present a decentralised scheme that facili- tates reliable network wide broadcast messaging without the requirement of strict time synchronisation, for duty-cycled low-power wireless embedded systems. In this emergent broadcast slot (EBS) scheme, devices coordinate their wake- up periods with their neighbours to exchange schedule infor- mation locally. This leads to the emergence of local slot syn- chronisation without the need for either network-wide syn- chronisation or a centralised time synchronisation element. We theoretically show that this scheme converges faster than similar emergent and gradient-based approaches, which we confirm by evaluation on real test-beds. We also show that our scheme exhibits lower overheads while being more tol- erant to disturbances caused by faulty nodes, wireless link failures, contention and interference in presence of deter- ministic propagation delays.