Use CSS mask and get a fancy Zig-Zag, Scooped, Scalloped, or Wavy borders!
.box {
--mask: conic-gradient(from -45deg at bottom,#0000,#000 1deg 90deg,#0000 91deg) 50% / 60px 100%;
-webkit-mask: var(--mask);
mask: var(--mask);
}