We describe the rationale for- and content of- a freely available, novel, theoretically driven and evidence-based approach to improving the teaching of word reading in reception classrooms called 'Flexible Phonics'. Flexible Phonics (FP) adds measurable value to-, rather than wholly replacing, existing synthetic phonics programmes. The rationale underpinning the FP approach concerns the need for multi-componential, maximally efficient, and truly generative approaches to allow early independence in reading for all children that apply to all words in the opaque spelling system of English. Building from these three principles, contemporary reading theory and evidence from cognitive science, linguistics and scaled educational implementation research, FP embodies a 5-element intervention differentiated to children's current attainment levels. FP augments mandated synthetic phonics through use of quality real books allowing 'Direct Mapping' of taught grapheme-phoneme correspondences, targeted oral vocabulary teaching, strategy-instruction on 'Set-for-Variability' and targeted preventative intervention for the most at-risk readers to then access wider FP content. Implications for policy and enhanced professional practice in English schools are considered.