It's NOT about that base, 'bout that base

I have often seen people asking how to remove the built in bases on the older plastic Mantic models. The newest plastics no longer have them.

I see these as both good and bad.  I like models that have a solid connection to the base - and having it molded on does this.  It fits into the square Mantic bases as well - almost as if it were designed for this :-).  However if you don't want to use the Mantic bases then these either result in a large 'bump' in your base or you have to remove them.

For my abyssal dwarf army, I've been doing volcanic bases - so it means I need to remove the plastic base from all my (abyssal) dwarf and (slave) orc models.  The method I use is straightforward, quite simple and easy to do, so I thought I'd go into way more detail than you actually need for it.
Of course you need a model with the attached round base.  Next you need your handy dandy sprue clippers, and maybe a model knife if you need to do any final cleanup.  Most sprue cutters have a flat side, which is important.

What can make removing the base difficult is if, for some reason, you feel you need to actually preserve the base.  When cutting apart models for conversions this is often true, but in this case, I feel at least, that the base is going to be thrown away, so it can be destroyed with no issues.

The idea here is that you can destroy the base in order to preserve the model itself - this is what makes it so easy.

The key here is to use the clippers to clip off the base around the feet, eventually leaving a small tab on each foot - which can then be easily clipped off as well.  The base is destroyed, but the model we care about is just fine.

Simply begin by cutting a bit 'line' into the base, on the inside of a foot.  For all of these, keep the flat side of the clippers next to the feet because you don't want to damage them.

Then reverse the clippers and do the same thing on the inside of the other foot.
If your clippers are long enough, both cuts will meet and you will have a decent chunk gone. If not, feel free to twist what remains off.

Now go around the side and back of each foot cutting with the clippers next to it.

If at any time you have a chunk of base get in your way - just clip it off.

What you want to get to is just 'tabs' under each foot.

You may want to trim these down to make it easier to clip off - again keeping the flat of the clippers against the model - but now you are clipping at an angle.  The goal here is to get a small enough piece under each foot to remove with a single clip.

Then simply snip off the remaining bit of base, now with the flat of your clippers against the bottom of the foot.

And with that you have removed the base - which now lies in a pile of small pieces in your lap :-). So do this over a trash can, or something to catch the pieces so you can dispose of them later (they are recyclable - so throw them with your empty sprues in your recycling bin!)

This technique is very quick and easy for most models, however Mantic does make one that is a bit more difficult.  The dwarf with the cloak model is more challenging.

This is because most of the base is fully molded onto the cloak - so you can't just clip around the feet anymore.  While I have tried it - a jewelers saw may be easier to just cut across.  But since I have the clippers out anyway . . .

You start with the easy part, clipping off a triangle in the front.

Then I start clipping away at the rest.  Keep the flat of your clippers against the model and dig into it a bit.

You won't get much with each single clip, but with each one you will get a little more.  I often find I want to cut of these chunks as I kind of peel the base off.

Eventually you will have the base off, though you may need to dig in a little to get it all.  At this point you may want to use your hobby knife to clean the cut a bit, or even a file if it is crucial that the bottom is completely flat.

And with that, even the harder piece is done.

I did a dozen of these in about half an hour while watch the American Ninja Warrior finals on tv (it would have been faster but I kept posing to take pictures).

Next is assembling the rest of the models - these are decimators, so I get the fun metal conversion bits that don't quite fit right, so you have to carefully bend each of them.  (I am really looking forward to the day Abyssal Dwarfs get ALL their own models, instead of re-using dwarf bodies).

Because it is all fun and games . . .