The 90 degree bend on a handle works great. Not only does it serve as a visual and tactile aid for billet indexing while forging, it can be used to help accurately clock resquares for mosaics, and affords a lot more control over the billet when forging.
As for can aspect ratio... I've done a lot of flat-can welding. Tray type mosaics or canoes as some call them, where a lot of small straight-edged pattern elements can be combined with or without powder to form what is effectively a monotile that will be displayed on the knife in the same orientation that it's assembled into the final billet. I.e. a side-grain mosaic. It works well, if you get some things right- the larger and flatter your dies the better. I do it on a hammer, my dies are 4x11" which is ideal but if yours are smaller just try to get as much billet surface area as possible on the die at a time and cover the entire surface evenly with as few blows as possible. What you want is for things inside to upset weld into each other, more than draw in any particular direction. A good 5 min soak AT welding heat between the first few heats really helps as well. Also you want to keep it hot, don't forge it below a welding heat during the first few short heats. If you meet all of those conditions you can really get a good clean piece of steel from the process. Including edge bars inside the can, with the flat sides being made of say .070" 15n20, can really helps the sides remain stiff and restrain the contents during welding. They can be hardenable patterned material, or sacrificial material to be removed afterwards.
I tend to do this and weld the can up to the contents under the hammer, then grind off, rather than resist it with paint or used foil. I think the can provides better support for the contents if it welds to them- then I throw it on the belt mod surface grinder and rip it off with 36 grit. Pretty easy that way. Check my Youtube if you wanna see all of this done with further explanation.
