The area of any shape can be found by counting unit squares that cover it. For shapes with irregular edges, students estimate by counting whole squares and combining partial squares. This bridges from concrete counting to the idea that area is a number of square units.
Provide grid paper and irregular shapes (drawn on or physical). Have students count whole unit squares and identify/count partial squares. Practice estimating and refining estimates.
You already know how to find the area of a rectangle by counting unit squares — or by using multiplication as a shortcut. Now you are extending that idea to shapes that are not nice rectangles: blobs, L-shapes, irregular outlines, and anything with a curve or a jagged edge. The definition of area has not changed: area is the number of unit squares needed to cover a shape completely, with no gaps and no overlaps. What changes is that a shortcut like length × width no longer works, so you have to go back to the original counting idea.
On grid paper, the strategy is to start with the easy part: count every whole unit square that falls entirely inside the shape. Give each one a checkmark so you do not lose track. Then look at the leftover spaces — the partial squares where the boundary of the shape cuts through a square, leaving only a piece of it inside. These partial squares are where estimating comes in. A common approach is to pair them up: two halves make roughly one whole square. A piece that is clearly more than half counts as one square; a piece clearly less than half gets ignored or paired with another small piece. You are not getting an exact answer — you are getting a reasonable estimate, and that is appropriate for irregular shapes without perfect measurements.
The deeper idea here is that area is a continuous quantity, not just a multiplication fact. Any region — no matter how oddly shaped — has an area, because you can always imagine tiling it with tiny squares and counting. This is actually how calculus eventually defines area, but right now the grid approach gives you the same fundamental intuition: cover the shape, count the tiles. The boundary line determines what is "inside" and what is "outside," and everything inside contributes to the area. Nothing about the boundary itself — its length, its jaggedness — directly tells you the area, which is why perimeter and area are two completely different measurements of the same shape.