<button class="btn">Кнопка</button>
<button class="btn2">Кнопка</button>

.btn 
{
  padding: 13px 38px;
  background: none;
  border-image: linear-gradient(45deg, transparent 10%, orange 10%, orange 90%, transparent 90%) 22 fill / 13px;
}
.btn2
{
  padding: 13px 38px;
  background: none;
  border-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'%3E%3Cpath d='M2 80 V2 H80 L98 20 V98 H20 Z' fill='red' stroke='black' stroke-width='4'/%3E%3C/svg%3E") 20 fill / 15px;  
}