<div class="block"></div>

.block
  height: 100vh
  width: 100wv
  position: relative
  &::after
    background: repeating-linear-gradient(45deg, #fff , #fff 10px, #3C7AB8 0, #3C7AB8 20px, #fff 0, #fff 30px, #CB2C4B 0, #CB2C4B 40px)
    position: absolute
    top: 0
    left: 0
    height: 100%
    width: 100%
    content: ""
    z-index: 0
  &::before
      background-color: #fff
      position: absolute
      top: 10px
      left: 10px
      height: calc(100% - 20px)
      width: calc(100% - 20px)
      content: ""
      z-index: 1
      border-radius: 20px