This article describes in details on how to create an L1 on Avalanche with Starter or Pro plan on either Testnet or Mainnet with Advanced Setup.
Customers can create an L1 on Avalanche directly with AvaCloud Portal.
After customers click on the Testnet on the screen above, they are given choices of Testnet Starter, Testnet Pro and Testnet Enterprise.
There are similar plans on Mainnet, including Mainnet Starter, Mainnet Pro and Mainnet Enterprise.
This article use the screenshots when creating an L1 on Testnet.
There is a separate article focusing on creating an L1 with the Testnet Starter/Free Trial plan. This article focus on the Testnet Pro and Mainnet Starter and Mainnet Pro.
Subscription payment
After Testnet Starter Pro is selected, customers are navigated to the Stripe screen to pay for the plan.
After payment, customers are redirected back to AvaCloud Portal to create an L1. It presents choices of Basic Setup and Advanced Setup. This article focuses on the Advanced Setup which allows customers to fine tune every configurations. 
L1 set up
First, AvaCloud needs to make sure Avalanche Testnet is connected. (Note: on Mainnet, it would ask customers to switch to Mainnet.)
Then customers can go through a series of screens to set up their own L1.
General information
Interoperability
Customization
Transaction manager
Contract manager
Native token minter
Rewards
Fees
Review of all customization by precompiles
Initial native token supply
Control keys
Customers can specify multi-signers to sign transactions for creating the L1 blockchain.
Region for nodes
Summary for review
After "Create L1" button is clicked, customers are shown a series status screens before being navigated to the Blockchain List page.
Customers will receive an email when the blockchain is ready to use. They can log into the AvaCloud Portal and they can see the newly created blockchain with detailed info.
Here is the video for the whole process