Why do this problem?
is excellent for helping to reinforce the properties of squares and in particular for highlighting the fact that a square is a square no matter what orientation it is in.
You could introduce this activity by showing the children a square piece of paper. Put the square on the board so that its sides are parallel to the sides of the board and ask the class what shape it is. How do they know? Then, invite one pupil to come up and pin the square on the board in a different way. Is the shape still a square? You might find that an interesting discussion ensues! It
is common for children to call a tilted a "diamond" but the earlier we can encourage them to avoid this, the better.
Once pupils have tried the problem (whether on paper or using the interactivity), they could show each other their completed squares and discuss the drawings before sharing them with you and/or the whole class. Playing the game Square It
would be a good way to end this lesson.
What do you know about squares?
What do you need to add to this to make it a square?
You could give some learners a grid (for example $3$ by $3$ small squares) and challenge them to draw all possible squares on it, if all corners have to be on the grid.
Children may need rulers to convince themselves that the sides of the shape they have drawn are (or are not!) the same. Turning the page also helps!