Newton is frequently seen as the founder of Western science. Was he the first person to explicitly articulate the scientific method?
NO. See at least :
René Descartes with Discours de la méthode. Pour bien conduire sa raison, et chercher la vérité dans les sciences (Discourse on the Method. An introduction to the Essais, which include the Dioptrique, the Météores and the Géométrie) (1637).
Note : "scientific method" is a vague concept: it is a "recipe" with various ingredients: observation, experiments, hypotheses, mathematization.
Observations, for example, are as old as mankind: for Europe, they date back at least to Ancient Greece : see Presocratic Philosophy.
The peculiar mixture of the ingredients is an Early Modern invention: we can find it fully mature into Newton's works, but Newton relies heavily on Galileo and Descartes.
No not in Europe. But scientific method has its roots in the Islamic World. The origins of the scientific method hearken back to the Islamic World, not the Western one. Around 250 years before Roger Bacon expounded on the need for experimental confirmation of his findings, an Arab scientist named Ibn al-Haytham was saying the exact same thing. He not only was a precursor of the scientific method (both theoretically and in practice), but he was well-known in Europe (as Alhazen or Alhacen) since the Middle Ages and influenced many European thinkers such as Bacon himself, Galileo, Kepler, Descartes and others. In other words, he was not an isolated antecedent, but an influential precursor.