I don't know the correct sizes, grid, or anything
The size and grid is dependent upon whatever modeling program you are using. Experiment and figure it out yourself.
For reference a 1x1x1 brick is a 1x1x1.2 box in Blender.
To make a brick you need to make a model with the following:
- Mesh model - named anything besides COLLISION or BOUNDS
- Collision box(es) - named COLLISION1, COLLISION2 etc (can have 10 boxes, must be exact boxes)
- Bounding box - named BOUNDS, should align to brick grid and people will not be able to build other bricks inside this
Note: You can leave out the bounding box and the converter will use the outer edges of your model to generate the bounds.
Then export the model as a .obj and use
Badspot's obj2blb converter to make your brick. View the topic for how to name bricks to get specific colors and whatnot.