Adding blocks should stem from your child theme and be included in your seeds so that the original theme structure can be restored if needed. Follow the Seeding Themes documentation to seed your alterations to the blocks. You can edit the blueprints directly in the app/blueprints folder, but it's not recommended if you plan on updating the theme.
From this point forward, it is assumed that you are creating blueprints in your seeds folder and seeding it from there.
Adding Your block to The Builder
Adding your block to the builder and columns group
To add your block to the builder group, you'll first need to create your own mixin content blocks within the seeds/blueprints/content/mixins/builder/ folder.
The following assumes you created a custom_block folder inside the above folder. This folder should contain the following files
Once you've created your custom block blueprint files, you'll need to add them to the Section and Column areas which are in the builder.yaml and section.yaml blueprint files respectfully
builder.yaml
uuid:78650dea-607e-4c63-bde8-2364cb786072handle:Content\Buildertype:mixinname:Builderfields:builder:type:repeaterlabel:BuilderdisplayMode:builderspan:adaptiveprompt:Add a Blockgroups:#...custom_block:name:Custom Blockicon:icon-toggle-ondescription:Your Custom Block DescriptiontitleFrom:titleuseTabs:truefields:hero:type:mixinsource:Content\CustomBlock
section.yaml
uuid:1be4d611-a49d-11ed-9116-3a678152e91chandle:Content\Sectiontype:mixinname:Sectionfields:section_header:type:mixinsource:Content\SectionHeadertab:Generalreverse_columns_on_mobile:label:Reverse Columns on Mobilecomment:Useful if you have content that needs to be stacked a different way on a phone.type:switchtab:Generalhr_1:type:rulertab:Generalcolumns:label:Contenttype:repeatercommentAbove:Create content for this section. Each content block uses it's own column. Max of 4 per section.span:fulldisplayMode:buildertab:Generalgroups:#...custom_column_block:name:Custom Blockicon:icon-toggle-ondescription:Your Custom Block DescriptiontitleFrom:titlefields:custom_column_block:type:mixinsource:Content\CustomBlock#...
Once done, you should see your block within the builder after you run:
phpartisanoctober:migrate
Displaying Block Content
Awesome, your block is in the builder. Now it's time to render it's content. You'll need to create some partials under builder/sections and builder/columns to prep the content for rendering.