Hi Eric,
I've recently worked with these from code, and what worked for me was following this blog post.
To control what gets displayed in the UI list view, I use the following attribute on the property:

[ListItemHeaderProperty(nameof(MyBlock.Title))]
public virtual IList<MyBlock>? MyBlocks { get; set; }

When building the list, I use contentRepository to create new blocks. Refactoring your example, it would look like this:

var page = contentRepository.Get<MyPage>(pageReference);

// Create your blocks
var block1 = contentRepository.GetDefault<MyBlock>(pageReference);
block1.Title = "First Block";
block1.Content = new XhtmlString("<p>This is the first block's content.</p>");

var block2 = contentRepository.GetDefault<MyBlock>(pageReference);
block2.Title = "Second Block";
block2.Content = new XhtmlString("<p>This is the second block's content.</p>");

page.Blocks = new List<MyBlock> { block1, block2 };

contentRepository.Save(page, SaveAction.Publish, AccessLevel.NoAccess);

From what I understood from the blog post, this is the recommended way to build the list. However, there's a minor caveat: when the page is being created for the first time, it won’t have a valid content reference yet. So, calling newPage.ContentLink will return a null reference, and passing that to contentRepository.GetDefault<MyBlock>(newPage.ContentLink) will throw an exception.

In that case, you’ll need to first save the page with simple properties only. Once it has a valid ContentLink, you can then add the list of blocks and publish it again.