This 2022 article provides extensive details of the steps involved in a robust scale (measurement) study -
Syed Mahmudur Rahman, Jamie Carlson, Siegfried P. Gudergan, Martin Wetzels, Dhruv Grewal. (2022). Perceived Omnichannel Customer Experience (OCX): Concept, measurement, and impact. Journal of Retailing.
Open access; freely available at https://doi.org/10.1016/j.jretai.2022.03.003
See Table 1 for an overview of the steps.