Hmm, you want to create a new map. Hmm ... But there's something to do with that. hmmm ... What do you know?
You can't do without a graphics program. You won't do anything without a bitmap base. Because the Dragon and UO Landscaper, the only two programs that exist for it, create maps (map0-5. Mul) from a bitmap image.
Honestly. Dragon is an older and simpler program. But UO Landscaper is better. Both need matrix bmp images to create maps. You will find the instructions here at ServUo. Enter UO Landscaper or Dragon in search.
However, you need something in the graphics program. Adobe photoshop, gimp etc. That's up to you. You have to know something.