“从头做起”常见的英文表达有 "start from scratch" 或 "begin from the very beginning"。
"start from scratch" 是一个常用的短语，意思是从零开始，不依赖已有的基础或条件，重新开始做某事。例如：
We're going to have to start from scratch and rebuild the entire system.（我们将不得不从头开始，重建整个系统。）
"begin from the very beginning" 则更直接地表达了从最开始的地方着手，强调起点的重要性。例如：
To master this skill, you need to begin from the very beginning and practice consistently.（要掌握这项技能，你需要从头开始，并持续练习。）