frame

frame.scad

difference() {
linear_extrude(10)
  hull()
    for (t=[[0,0], [60,0], [60,40], [0,40]])
      translate(t) circle(4);
  
translate([0,0,2]) linear_extrude(10)
  hull()
    for (t=[[5,5], [55,5], [55,35], [5,35]])
      translate(t) circle(4);
}

frame2.scad

module base() {
    difference() {
    linear_extrude(10)
      hull()
        for (t=[[0,0], [60,0], [60,40], [0,40]])
          translate(t) circle(4);
      
    translate([0,0,2]) linear_extrude(10)
      hull()
        for (t=[[5,5], [55,5], [55,35], [5,35]])
          translate(t) circle(4);
    }
}

minkowski() {
  base();
  sphere(2);
}