Wojciech
Here's what I would suggest
Take a look at the source of any of the blockly demos , for example
https://blockly-demo.appspot.com/static/demos/fixed/index.html .
Copy the source to a local file or any file on your webserver.
Then, in the file do the following ..
1) Adjust the javascript script tags to point to your location of Blockly.
<script src="my/location/wherever/blockly_compressed.js"></script>
2) Add your own javascript files for your custom blocks . The block factory should have given you the rudimentary javascript.
<script src="my/location/wherever/my_custom.js"></script>
3) Add your custom blocks to the toolbox.
<xml id="toolbox" style="display: none">
<block type="standard_block1"></block>
<block type="my_custom_block1"></block>
<block type="my_custom_block2"></block>
</xml>That is all there is to it.
You could choose if you want to make your Blockly fixed size or resizable. Just pick the right html file to start with and change a few things.
Later you could make categories within the toolbox to add standard and custom blocks in a neater way. Furthermore, you could now make blockly generate the code for your blocks.
Hope this helps.
Regards
Avi