If you're looking to design your own medals online with a hollow out design and custom engraving, you can explore various options provided by custom medal suppliers. Here are some steps you can follow:

1. Research Custom Medal Suppliers: Look for reputable custom medal suppliers that offer online design tools or services. You can search online or get recommendations from others who have previously ordered custom medals.
2. Choose a Supplier: Select a supplier based on their reputation, customer reviews, pricing, and customization options. Make sure they provide the specific features you need, such as hollow out design and custom engraving.
3. Access Online Design Tools: Once you've chosen a supplier, check if they offer an online design tool. This tool allows you to personalize your medals by selecting the shape, size, material, and other design elements.
4. Hollow Out Design: If you want a hollow out design for your medals, look for options within the design tool that allow you to incorporate this feature. It may involve creating cut-outs or empty spaces within the medal's design.
5. Engraving Options: Explore the engraving options available. Some suppliers might provide engraved text or images, while others may offer sublimation printing for more intricate designs. Ensure that the supplier can accommodate your engraving requirements.
6. Material Selection: Choose the material for your medals based on your preferences and budget. Common options include metal alloys like brass or zinc, which can be coated with gold, silver, or bronze finishes.
7. Submit Your Design: Once you've finalized your medal design, submit it through the supplier's online portal. Make sure to review the design carefully before placing your order to avoid any mistakes.
8. Quantity and Order Details: Specify the quantity of medals you require and provide any additional information, such as delivery address and desired timeline. The supplier will calculate the cost based on these details.
9. Confirm and Pay: Review the order summary, including the design, quantity, and total cost. If everything is correct, proceed to payment using the supplier's preferred method.
10. Production and Delivery: After you've placed your order, the supplier will begin production. The time it takes to complete the medals will depend on the complexity of your design and the supplier's production capacity. Once ready, the medals will be shipped to your specified address.

Remember to communicate with the supplier throughout the process if you have any questions or require assistance.