To make the base of the globe we need a bit more room. Open a new image 400x400, into which we can transfer the globe.

Click on the globe image frame to make it current. Use the standard selection tool, set at circle 280x280, with fixed size checked. Place the cursor at 0,0 and click to select the globe.

Click on the copy button (left of the pair shown here), and then click on the frame of your new empty image to make it current. Finally, click on the other button of this pair, the paste button, and an object copy of the globe will appear in the new image. Move it to the top centre of the image, and then use Edit/Selection/Merge all.

Using the selection tool, set at rectangle and with fixed size unchecked, select a rectangle at the base of the globe. The rectangle should cover roughly a quarter of the bottom of the globe, not more than a quarter, and it must stick out a little bit on either side of the globe.
 

Click copy, then paste, so that a second (object) copy of the selection is placed on top of the image. Move this top copy down below the globe so that you have room to work on it.
 

Use Edit/Convert Object Type and convert from Image to Path.

Click on the path tool and then change the Mode to Path. Your rectangle will be filled with white and surrounded by a second rectangle. The little black squares on this outer rectangle are 'handles' with which you can distort the shape.
 

Place the cursor on the top left corner handle, and it will turn into a crosshair. Click and drag the corner upward a little way, so that the top edge of the rectangle curves. Be careful to keep the vertical side straight. Then do the same with the top right handle. The two handles on the top side have now dropped below the edge. They can be used to adjust the shape of the curve if necessary.

Now do the same with the bottom two handles, so that the curved top and bottom edges are more or less parallel, and the side edges still straight. When you are satisfied with the shape of the base, change the path Mode to 2d object.

Click on the colour rectangle to the left of Mode and change the colour to black.

Use the pointer tool and move the base up onto your snow globe.

You can now crop away the surrounding white space, leaving your snow globe at its final size. The picture on the right shows the base in position and the image cropped. Use Edit/Select/Merge All to fix the base to the globe permanently.

Later on we are going to need to select just the visible part of the globe in order to add the snow, and now is a good time to store the selection, before we have added any more to the base.

Use the selection tool, set to Mode new and Circle 280x280, with fixed size in pixels checked. Click in the top left corner of the image, to give you a selection marquee the size of the globe. Put the cursor inside it, hold down the left mouse key and move the circle till it exactly fits round the globe. It will extend into the base where the globe is now hidden. While the mouse button is held down you can use the keyboard arrow keys for one pixel fine adjusment.

Use Edit/Selection/Invert. You will see that the circle still extends down into the base. Change to the magic wand tool and the settings below.

Click on the base, inside the circle area. The part of the base inside the circle will be selected - and so will part of Santa's boot, but we will put that right in a minute. Use Edit/Selection/Invert again, and just the visible part of the globe will be selected.

Now we need to include Santa's foot. Select the Selection Lassoo tool (shown outlined in red in this picture) and set the settings as shown here.
 

Zoom in so that you can see what you are doing. Click once with the lassoo tool where each of the red x's are, starting at the left and working along to the right, and then twice where the yellow one is. The selection marquee will then run along the top of the base and Santa's foot will be included in the selection. If your line across the base is a bit wavy, click the Undo button and do the selection again until you are satisfied with it.

Use Edit/Selection/Copy Selection to Object Library, and this dialogue box will appear. Ensure that the options are correct - you will have to give the selection a name - and click OK. We can now retrieve the globe selection whenever we need it.

The base looks two dimensional because only the front exists. We have to do some freehand drawing now to show the back of the base. Use Edit/Selection/None. Set the foreground colour to bladk

Use the paintbrush tool, Shape circular 2, Transparency and Soft Edge both 0 and Preset none.

Zoom in so that you can see what you are doing, and draw a curved line between the corner of the base and the side of the globe. Inside this curve, fill the white area with a dark grey. Do the same at the other side of the globe.

The globe itself is now finished, and all that remains is to add the snow, make the frames, and animate it.