Guidance on Building a Blue-Team Cybersecurity Portfolio

How can I build a blue-team cybersecurity portfolio? The user is a job seeker with experience in L1/L2 incident response during an internship and is interested in blue-team cybersecurity. They are looking for advice on building a blue-team-focused portfolio, including relevant tools, labs, projects, or topics. They acknowledge the importance of real skills over claims and want guidance on demonstrating those skills.