Alakihel:
Hi everybody ! First of all I wish you a happy new year for 2012 ! I wish you a lot of new chaos dwarves miniatures and a lot of fights and a lot of kicked ennemies !
Then I have a question, I’ve reiceive my Forgeworld warmachines, but I’ve get a problem.
I want to make a base for the warmachine (magma canon) but I want to make a hole to put the crew (which are already on a base)
Like on this picture :
Thommy H:
I did something similar, but nowhere near as good, with my Hellcannon. I put it on a regiment base (one with raised sides all 'round - not sure if they make them any more) and just glued layers of card into it with the spaces for the crew cut out until it reached the height of the sides. Pretty simple. 
Grimbold Blackhammer:
My camera is unavailable so I’ll try and describe how I did it. It is a fairly simple process but takes a few steps.
I use GW movement trays so make it big enough (with the tray edges) to hold the model and crew plus whatever scenery you want on the base. My Hellcannon for example is on a 140mm square base though for other models you’ll be restricted to whatever base size it is supposed to be on.
Cut a piece of plasticard to fit insidethe movement tray.
Cut a piece of cardboard from a cardboard box (not a cardboard package, I’m referring to the three-ply cardboard big boxes are made from). Tear off one of the three layers of the cardboard so you are left with a flat side attatched to the wavy middle. Glue the flat piece of the cardboard to the plasticard you just cut. This should put the plasticard top level with the top of the movement tray when you put it in.
At this point you have to decide how your models will be positioned and cut out the little squares for the bases in the plasticard/cardboard base. If you’re ambitious I like to use Rare Earth magnets on the corners of the plasticard and the corners of the movement tray to hold the plasticard in place. Technically you could probably just glue the cardboard side down to the movement tray.
Spray it with primer, glue your model onto the plasticard, and do your bases however you want (lava, bunnies, whatever…).
Put your model on the table and watch your friends “ooooohhhh” and “awwwwwwwwwhhhh” over your awesome bases!
Grimbold Blackhammer
Alakihel:
Why not, I’ll check this right now, Thanks for the advices 
Abecedar:
Have never had or used plasticard, so I use MDF of varying thicknesses. usually the bigger the model the thicker the base. Figure out your size and cut a piece for the base plate. To build up the edges I use the long matchsticks from supermarkets, glued to the edges. The matches are just the right height for the ground level to be right on a model. So where-ever the model men are not, then I build up those bits with more 3mm MDF cut to fit (normally just scraps) and then fill in the gaps and go from there.
Ishkur Cinderhat:
It’s been a long time by now, but I think I simply used a regimental base (from the kit with the modular ones that you can cut and glue to a suitable size) and filled it with single unit bases. What can I say, it sure wasn’t cheap but then Chaos Dwarfs never are. 
Alakihel:
Yeah this is what I thought because when you take a well attentioned look at the bae, you can see the little space between two bases!
I stole the idea for mine !