You need to really pack the mixture into the ice cream scoop when portioning these macaroons out onto the baking tray. If you don't they won't hold together securely and could crumble. The macaroons can also be crumbly and fall apart if you don't measure the ingredient accurately, change any of the ingredients (even a small change) or if you use the wrong type of shredded coconut. It absolutely has to be finely shredded.