While Etch is still in its early days of development, some of the features are not fully baked and some help is needed. One of these is the custom fields interface in a post. Fortuantely, a couple of lines of CSS is all you need.

.inside {
    display: grid;
    gap: 1em;
}
.field {
    display: grid;
    gap: 0.5em;
    grid-template-columns: 1fr;
}

.inside {
    display: grid;
    gap: 1em;
}
.field {
    display: grid;
    gap: 0.5em;
    grid-template-columns: 1fr;
}

As you can see in these screenshots, it is a positive change.