It's difficult but not impossible to start on a steep hill in a very low gear. There are tricks to learning how to do it is all. One method is to hold the front brake on with your dominate foot at about the 2 o'clock position. Push down on the pedal, hop up on the saddle and release the brake all at the same time. It's a little complicated but possible. Clipless pedals help since you can pull up with your rear foot to add some oomph to the pedal stroke.

If you have a rock or curb handy, you can put one foot on the curb (or rock), put pressure on the front pedal, hold the front brake and then push on the pedal and release the brake at the same time. No need to hop up in the saddle.

If you have a tree handy, you can put both feet in the pedals, hold the tree with one hand and the brake with the other, then just release the brake, release the tree and pedal. Easy peasy.

These are all things that mountain bike riders do on a regular basis on trails that are about 20 feet narrower, much steeper and much rockier than you'll find in normal touring. An afternoon of mountain biking will teach you all these skills...slow speed riding, slow speed starting and how to start on an impossibly steep hill...in about 3 hours. You'll even learn how to ride at 3 mph while climbing over rocks which is not something you encounter on most bicycle tours.