Pencil used to by my go-to tool, but over time it has slowly grown more complex and less useful. More recently, I am using Google Slides for quick GUI prototype

Pencil used to by my go-to tool, but over time it has slowly grown more complex and less useful. More recently, I am using Google Slides for quick GUI prototypes - if I need something more robust, I hire a designer, but my necessity for solid wireframes as a communication tool is low enough that it's not worth learning a new tool.