As I have mentioned in this post, the key to reconstructing the Altar of Burnt Offering lies primarily with properly reconstructing its Copper Grate (Mesh).
Here is another opinion on how this Grate might have looked like, from James Strong's book - "The Tabernacle of Israel in the desert". (this post)
As you can see, the Grate here is shown simply as a flat Mesh with four rings, that would be inserted into specially designed slot in the middle of the Altar (Exodus 27:5).
In my opinion, such design is not very good as the slot for the Grate would compromise the structural integrity of the Altar, not to mention that the Grate would not be secured properly and may fall out.
On the other hand, perhaps there is some truth to such design because the Grate here would be relatively light and easy to handle.
Unfortunately, I'm yet to figure out what proper design would suit the description of Exodus 27:4-5 best.
P.S. Perhaps, the Grate of the Altar of Burnt Offering looked somewhat like this:
This image of the Brazen Altar is from templebuilders.com web site: