SOURCE

function setup(){
    createCanvas(400,400);
    background(255);
}
function draw(){
    for(let y =0;y<height;y +=20){
        for(let x = 0;x <=width; x +=20){
            fill(235,90,58);
           ellipse(x,y,18,18);
        }
    }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.1.9/p5.min.js"></script>