Fixes #2939: documented the process of creating your own application template

docs/guide/apps-own.md

 Creating your own Application structure
 =======================================
 
-TBD
\ No newline at end of file
+While [basic](apps-basic.md) and [advanced](apps-advanced.md) application templates are great for most of your needs
+you may want to create your own application template to start your projects with.
+
+Application templates are repositories containing `composer.json` and registered as Composer packages so you can make
+any repository a package and it will be installable via `create-project` command.
+
+Since it's a bit too much to start building your template from scratch it is better to use one of built-in templates
+as a base. Let's use basic template.
+
+Clone basic template repository from git
+----------------------------------------
+
+```
+git clone git@github.com:yiisoft/yii2-app-basic.git
+```
+
+And wait till it's downloaded. Since we don't need to push our changes back to Yii's repository we delete `.git` and all
+of its contents.
+
+Modify files
+------------
+
+Now we need to modify `composer.json`. Change `name`, `description`, `keywords`, `homepage`, `license`, `support`
+to match your new template. Adjust `require`, `require-dev`, `suggest` and the rest of the options.
+
+> **Note**: In `composer.json` file `writable` under `extra` is functionality added by Yii that allows you to specify
+> per file permissions to set after an application is created using the template.
+
+Next actually modify the structure of the future application as you like and update readme.
+
+
+Make a package
+--------------
+
+Create git repository and push your files there. If you're going to make it open source github is the best way to host it.
+If it should remain private, any git repository would do.
+
+Then you need to register your package. For public templates it should be registered at [packagist](https://packagist.org/).
+For private ones it is a bit more tricky but well defined in
+[Composer documentation](https://getcomposer.org/doc/05-repositories.md#hosting-your-own).
+
+Use it
+------
+
+That's it. Now you can create projects using a template:
+
+```
+php composer.phar create-project --prefer-dist --stability=dev mysoft/yii2-app-coolone new-project
+```