To make Alibaba's circular welcome sign in front of the door, you first need to prepare a circular base plate, which can be made of wood or plastic materials.

Then, paint the base plate with Alibaba's iconic color, which is dark blue. You can use spray paint or paint to color it.

Next, use white fonts or logos to write the words "Welcome" and "Alibaba" on the sign. You can use acrylic paint, stickers or spray painting to make the fonts.

Finally, fix the made sign in a suitable position in front of the door. You can use screws, glue or hooks to fix it. This completes the production of Alibaba's circular welcome sign in front of the door.