Typically hazelnuts are washed, dried, sized, shelled, sorted, packed and pasteurized by processors. In order to process organic hazelnuts, processors will either require their own organic certification or sign an attestation of compliance. Attestations of compliance are generated for non-certifiable custom services including transport, storage, seed cleaning, etc. Signing an attestation means that they are familiar with all of the standards in terms of protecting the organic nature of the product (cleaning products, preventing any commingling of organic and conventional products, etc.) and promise that they have followed necessary steps to protect organic nature of the products. You can find more details here:
Organic products are sold into different markets by different methods. Typically organic growers are more involved in the marketing of their hazelnuts and will sell directly to consumers through farmers markets, box programs, or farm gate. While this does take more time, you are also much more in touch with market conditions.