.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: 100px;
  grid-auto-rows: 60px;
  grid-gap: 15px;
}

.col {
  background-color: tomato;
}

This creates 2 rows, first is 100px height, second is auto-created with 60px height. 2 columns in the second row have 1fr width.

Is this possible via CSS Grid/Flexbox to horizontally center 2 columns in the 2nd row? I.e. have a varying number of columns per row.

I am stuck trying to solve a trivial usecase for the CSS Grid framework in the browser. This is pretty nonproblematic to achieve if you build your grids with Flexbox.

But can I achieve it with CSS Grid?

Here is a CodePen demo of what I am trying to achieve.