Contrary to popular belief, you can have "incomplete" projects on your portfolio (especially if you are looking for projects to feature). Meaning that if your focus is a specific part of a larger project— for example, the form validation of a login page— you don't need to develop the entire login process. Just make sure you are thorough with your explanation and documentation of the specific part of the project you are focusing on. A thorough but incomplete project is better than a half-assed "complete" one.
UXfol.io’s Portfolio Template - Research-backed template, UXfolio discussed with 37 recruiters and multiple UX leaders. Below is a tldr; of good requirements. Projects should fit your future employers’ needs/ personal preferences, and should showcase your design process/ decisions. Don't just feature the final UI.
Cofolios - Case studies and portfolios from interns at top tech companies
21 Resumes from Case Study Club - Really great examples of successful resumes, with takeaways towards end of article
CareerFoundry - Very straightforward tips and guides
UXfol.io ‘s Guide - Has a fantastic step-by-step guide on how to write a UI/UX resume. Below is a tldr;