<h3>United Kingdom</h3>

<div class="flag united_kingdom">
  <div class="united_kingdom__plus">
    <div class="plus"></div>
  </div>
  <div class="united_kingdom__x">
    <div class="x__strip-1"></div>
    <div class="x__strip-2"></div>
  </div>
</div>

* {
  box-sizing: border-box;
  margin: 0;
}

body {
  width: 100%;
  height: 100vh;
  background-color: rgb(221, 239, 255);
  display: grid;
  place-items: center;
  font-family: cursive;
  font-weight: bold;
}

h3 {
  position: absolute;
  text-align: center;
  top: 20px;
}

/* Main Style Stars from here  */
.flag {
  position: relative;
  width: 300px;
  height: 200px;
  box-shadow: 0 0 1px rgba(0, 0, 0, 0.5);
  overflow: hidden;
}

.united_kingdom {
  display: grid;
  place-items: center;
  overflow: hidden;
  position: relative;
  background: #213064;
}

.united_kingdom__plus {
  z-index: 1;
  width: 100%;
  height: 100%;
  filter: drop-shadow(0 10px white) drop-shadow(10px 0 white)
    drop-shadow(-10px 0 white) drop-shadow(0 -10px white);
}

.united_kingdom__plus .plus {
  width: 100%;
  height: 100%;
  background-color: #e51837;
  clip-path: polygon(
    0% 43%,
    45% 43%,
    45% 0%,
    55% 0%,
    55% 43%,
    100% 43%,
    100% 58%,
    55% 58%,
    55% 100%,
    45% 100%,
    45% 58%,
    0% 58%
  );
}

.united_kingdom__x {
  position: absolute;
  inset: 0;
}

.united_kingdom__x > .x__strip-1,
.united_kingdom__x > .x__strip-2 {
  position: relative;
  background-color: rgb(255 255 255);
  height: 32px;
  transform: rotate(-28deg) scalex(1.3) translate(-30px, 73px);
}

.united_kingdom__x > .x__strip-2 {
  transform: rotate(28deg) scalex(1.3) translate(13px, 47px);
}

.united_kingdom__x > .x__strip-1::before,
.united_kingdom__x > .x__strip-1::after,
.united_kingdom__x > .x__strip-2::before,
.united_kingdom__x > .x__strip-2::after {
  position: absolute;
  background-color: #e51837;
  content: "";
  width: 50%;
  height: 10px;
}

.united_kingdom__x > .x__strip-1::before {
  bottom: 7px;
}

.united_kingdom__x > .x__strip-1::after {
  top: 7px;
  left: 50%;
}

.united_kingdom__x > .x__strip-2::before {
  bottom: 7px;
}

.united_kingdom__x > .x__strip-2::after {
  top: 7px;
  left: 50%;
}