How to use CSS grid to create 3x3 grid but place items in specific grid columns

Question

I'm trying to create a layout that looks like this:

The blue blocks are divs. It's essentially a 3x3 grid but with gaps in the 3rd and 4th grid column.

How can I create a gap within CSS grid to achieve this layout? I've tried it with flexbox, but couldn't achieve the above, so hoping a grid layout is the answer.

Here's my code:

.container{
  border: 1px solid;
  display: grid; 
  grid-template-columns: 1fr 1fr 1fr; 
  grid-template-rows: 1fr 1fr; 
  gap: 0px 0px; 
  grid-template-areas: 
    ". . ."
    ". . ."; 
}

.item{
  border: 1px solid lightgrey;
  padding: 10px;
}

<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
</div>

Answer 1

CSS grid allows you to choose which row and column an element will start in (and indeed, though not needed in your case, how many columns/rows it is to span).

This snippet gives the 3rd and 4th children of the wrapper specific grid positions.

.container {
  border: 1px solid;
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr;
  grid-gap: 10px;
}

.item {
  border: 1px solid lightgrey;
  padding: 10px;
}

.item:nth-child(3) {
  grid-column: 2;
  grid-row: 2;
}

.item:nth-child(4) {
  grid-column: 3;
  grid-row: 2;
}

<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
</div>

Note: just for a demo it has also introduced a non-zero grid-gap. The grid-area settings have been removed as not needed if the above method is followed.