I love the uniqueness behind DIY hides and although I have not got around to doing one for myself I have a few links to some good ideas
This website has a bunch of simple and creative ideas for hides that seem easy enough
http://petdiys.com/diy-stone-axolotl-hide/
If you really want to get into the diy spirit you can check out what this person did
My wifes 6x2x2 Axolotl aquascape step by step
If you are lucky enough to have access to a kiln then your imagination is the limit on any hide you would want to create. As long as there are no sharp edges, its big enough for the axolotl, it has been fired to the optimum Temperature and sealed with a waterproof glaze or nontoxic finish it should be suitable for your axolotl/s. Keep in mind I have also read that even kiln fired clay can wear away in water. While I am not entirely sure on the validity of that statement I believe it would be a good idea to check that out thoroughly before throwing homemade pottery into your tank.
Here is one idea that I personally liked
Also, if price is the main concern ebay and amazon.com have a few fake log like hides that are big enough for an axie and look nice in a tank for pretty cheap. I would check it out!
You could also always google search diy axolotl hides and check out pinterest ideas. (assuming you have not yet)
Although these ideas may not be the quickest they are decently cheap and a good investment for a beautiful unique hide.
Hope this helps x