const options = {
  method: 'DELETE',
  headers: {'X-Spree-Seller-Id': '<x-spree-seller-id>', Authorization: 'Bearer <token>'}
};

fetch('http://{defaultHost}/api/v3/seller/delivery_methods/{id}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

curl --request DELETE \
  --url http://{defaultHost}/api/v3/seller/delivery_methods/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'X-Spree-Seller-Id: <x-spree-seller-id>'