I call it a "surprise box" because each week there is something new. We have a special blanket that we sit on and we go through the box. I try to include a couple stories, a hands-on activity and a toy or puppet. The purpose is to focus on sitting still while we do an activity together. I usually pick a time of day where we need something to fill some time. I also try to include something new that she's never seen before. Don't over think it, just pull a few things together that connect together.
With young children don't expect to have them sit for too long. Keep it really simple. For older children you can include an independent reading or writing activity along with the surprise box.
Here are a couple examples of surprise boxes I've done with my 2-year-old:
Hands-on: Animal Matching game
Zebra puppet (I made in school)
Homemade zoo book about one of our visits to the zoo
Hands-on: Foam ABCs
Book: Alphabet Mystery by Audrey Wood
My daughter's name in foam letters on a laminated piece of paper
Hands-on: Color Book with rectangles
Books: Colors; Brown Leaf, Brown Leaf; Blue Hat, Green Hat Sandra Boyton
Zebra puppet (focus on an animal with two colors -- black and white)