One of the top structured YouTube resources for learning interior design from scratch is the Interior Design 101 10-part video series by The Interiorist Playlist. [1]
The Interior Design 101 Course Breakdown
Getting Started & Briefs: Writing a one-page home brief to act as a design compass (Ep. 1).
Balance: Distributing visual weight using symmetrical, asymmetrical, and radial balance (Ep. 2).
Scale & Proportion: Choosing object sizes, heights, and weights so the room feels cohesive (Ep. 3).
Rhythm & Harmony: Using repetition, progression, contrast, and transition to build visual flow (Ep. 4).
Contrast & Color: Guiding the eye and styling color palettes safely (Ep. 5).
Space Planning & Lighting: Laying out furniture flows and layering ambient, task, and accent lighting (Later Episodes). [1, 2, 3, 4, 5]
Other Recommended YouTube Channels for Design Basics
Robeson Design: Frequently recommended on interior design forums for breaking down a professional designer's thought process.