gistfile1.scss

@mixin my-component {
  all: initial;
  * { all: unset; }
}

@mixin my-box {
  @include my-component;
  display: inline-block;
  background: white;
  border: 1px solid black;
  padding: 10px;
}

.my-small-box {
  @include my-box;
  width: 100px;
  height: 100px;
}

.my-large-box {
  @include my-box;
  width: 200px;
  height: 200px;
}