basic css grid stuff
Codepen with staggering grid item sizes in a 3x15 : https://codepen.io/tiggle/pen/MZJxzg
.container {
display: grid;
grid-template-columns: 2fr 6fr 2fr;
grid-template-rows: 1fr;
display: -ms-grid;
-ms-grid-columns: 2fr 6fr 2fr;
-ms-grid-rows: 1fr;
.item1 {
grid-row: 1;
grid-column: 1;
-ms-grid-row: 1;
-ms-grid-column: 1;
}
.item2 {
grid-row: 1;
grid-column: 2;
-ms-grid-row: 1;
-ms-grid-column: 2;
}
.item3 {
grid-row: 1;
grid-column: 3;
-ms-grid-row: 1;
-ms-grid-column: 3;
}
}