If they get a chance to lay their eggs, we are going to have everything eaten flat with hoppers later on.
Context: People are trying to stop locusts to land on their farms. So they suppose that they are going to have everything eaten by them if these locusts get a chance to settle there. What the word 'flat' suggests here? what is the word class of the word 'flat' here? And what particular function does it play in this context?