Jack's Chain is a popular block with some challenging elements.
In this class Philippa covers :

Drafting the templates from first principles (for any size block) and creating the freezer paper templates.
Creating the nine-patches from strips including a review of colour/tonal choices.
Getting great results sewing 'Y' seams with pressing suggestions.
Assembling multiple blocks into a full quilt and drafting the final pieces to fit around the edges.