A pinboard is very useful for exploring all the possible four and five sided shapes. This may be simply made by nailing panel pins or small nails into a piece of plywood approximately 24cm × 24cm.
Cut out the plywood and mark a grid of lines at 2cm intervals in both directions across the plywood. Tap in the pins at the points where the lines of the grid meet. Leave enough of the pins protruding to accommodate elastic bands.
When exploring 2D shapes made up of squares , it is worth discussing what counts as a shape eg does joining two squares at the corner make a shape? What would happen if you cut it out?….. etc
Free Y2 maths worksheet: Making shapes using a pinboard (pg 1)