The canvas is your main working area for a watch face. All elements will be added to the canvas, and it can show you your watch face at different times (using the time machine) & modes. On the canvas you can drag your elements into position, resize, and rotate them.
The layer list contains all layers for your watch. The elements are listed in order from top to bottom as a stack. You can think about it as a stack of paper - elements at the top will cover up the elements below. From here you can drag and drop element's orders, toggle visibility, and rename/duplicate/delete elements.
The Facer Time Machine allows you to see your watch face in action. You can use this to preview how your watch will change throughout the day. Use the slider to drag to specific times, or view your watch face animations by using the play & fast-forward buttons.
Every element has an 'advanced' panel, which is where you can add tags, expressions, formulas, and more! The advanced section lets you get under the hood and build anything you can dream up in the Facer creator.
To know more about Tags, Expression and Formulas, please go here
Shape previews show your watch face as it will appear in various shapes and sizes of watches. In order to get the best exposure for your creations, make sure your watch looks great in both square and round formats, and preview how it will look on watches that have a 'chin' element at the bottom of the dial.