Simple grid

<!-- Row -->
<div class="row">
<!--Cell with given width. Replace 25% with whatever you want -->
<div class="row__cell row__cell--1/4">25%</div>
<!-- Cell that takes remaining width -->
<div class="row__cell row__cell--fill">
...
</div>
</div>
.row {
display: flex;
margin-left: -8px;
margin-right: -8px;
}
.row__cell {
padding-left: 8px;
padding-right: 8px;
}
/* Cell with given width. Replace 25% with whatever you want */
.row__cell--1/4 {
flex: 0 0 25%;
}
.row__cell--fill {
flex: 1;
}

See also

Card layout

Masonry grid