The Five Fingers scale is a great way to estimate using the tools mother nature gave us! Each finger is a different response or number.
Agile Estimation and Capacity Planning
Get to the point: A story of point systems for the UX portfolio, by Emily Femmer
12 Agile Estimation Techniques to Try With your Team
What is the standard size for Agile Team? - Quora
Sprint Poker by Parabol, Agile Estimation for the Remote Age
Agile Estimating: How Teams Estimate with Story Points
Agile Estimation: A Guide to Efficient Planning & Delivery
PI Planning - Scaled Agile Framework
Agile Effort Estimation Techniques: Ensuring Predictable and Successful Sprint Outcomes, by Yawar Osman, Jan, 2024
Agile Estimating: How Teams Estimate with Story Points