Grid layout issue with alternating two-item rows

I am trying to figure out a grid layout which always has 2 posts in row. I would like the first item in row to take about 1/3 width and second to take 2/3 width, however in next row it should be vice versa.

Here is a layout example

1/3 2/3
2/3 1/3
1/3 2/3
2/3 1/3

This shouldn't be hardcoded in anyway and should work with any amount of children.

I did try something like this and some similar solutions

.latest-posts-block {
        display: grid;
        grid-template-columns: 1fr 2fr; 
    
        &__post:nth-child(4n + 1),
        &__post:nth-child(4n + 4) {
            grid-column: 1 / 2;
        }
    
        &__post:nth-child(4n + 2),
        &__post:nth-child(4n + 3) {
            grid-column: 2 / 3;
        }
    }

I can't quite figure out how to solve this, maybe anyone has worked on this issue before

A demo from my article that I recommend you read: https://css-tricks.com/exploring-css-grids-implicit-grid-and-auto-placement-powers/#grid-patterns

.grid {
  display: grid;
  grid-auto-rows: 100px;
  grid-auto-columns: 1fr;
  grid-gap: 5px;
}
.grid :nth-child(4n + 1){
  grid-column: span 2;
}
.grid :nth-child(4n + 4){
  grid-column: 2/span 2;
}

/**/
.grid {
  max-width:600px;
  margin:auto;
  counter-reset:num;
}
.grid *{
  border:2px solid;
  font-size:30px;
  box-sizing:border-box;
  font-family:sans-serif;
  display:grid;
  place-content:center;
}
.grid *:before {
  content:counter(num);
  counter-increment:num;
}

<div class="grid">
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
</div>