I use a recycled apple juice bottle, the sort with indentations for a hand grip.  The squarish shape keeps it from rolling.  A short length of line with a small carabiner clipped onto a jackline rigged athwartships under the lip of the sternsheets (this in a Passagemaker) so it won't float off in a capsize.  I can generally get the cap off one-handed.

Aboard my PMD, I use an extra pair of open oarlocks to keep the oars up along the sides, secured with short bits of shock cord.  That would preclude hiking out, however, but I'm not a big fan of hiking out, anyway.

The electric motor is a puzzlement.  The NED really isn't designed to hang a motor, even a small electric, in any way in which it might be used effectively.  Maybe heel her over a bit and paddle her like a canoe in tight quarters, sorta like they'd do with Adirondack Guideboats?  I used to do this to good effect with a Sea Pearl 21, which is sort of dory-shaped, to good effect if it wasn't really windy.

.....Michael

   My dory is heavily modified but this may be of some use to you.

Going to windward I try to get well forward, thwart by daggerboard trunk if possible but it's a long reach for the tiller extension. On a run moving back to what you're calling thwart two gets the bow up a bit. I installed bench seats, they give me more seating flexibility. Figuring out your trim will help your tacking performance.

Hiking out: Not me brother. When heeling I just press one foot to the opposite side hull, up by the gunnel if there is a lot of heel. More than that I let go the main sheet.

Motor: Mine is a stand up paddle board paddle (batteries last and last). I stand up to use it, works a treat. Steering is hard, sometimes I stand on a cord tied to the tiller extension, but have looped it around my knee to steer with my leg.

8' oars fit between the bulkhead at daggerboard trunk and bow under breasthook. I prefer longer oars and did this:

You'll also see lots of drill/fill/drill holes in the bulkheads through which I tie cords to secure all kinds of things that could roll around and float away.

:: Where do you brace your feet when tacking?

I've never sailed solo, so la capitaine sits on thwart 3 while I chill by the rudder. Back there the boat is narrow enough I put my feet on the side of the boat.

:: Does anyone hike out when tacking?

Not while sailing the dory!

::Any ideas for where to stow a bottle while sailing so it doesn't roll around?

We bring an old duffle bag or something like that. I recently bought some pouches that i attach to my belt for my phone, garmin, camera, etc. Search molle pouch on amazon.

::I have a small electric trolling motor. Any ideas about how to mount on the Dory?

If you search this site there's a picture of someone who did what you suggest, kind of clamped on. I wonder if a thwart like the mast thwart could be built at the back which could be removed when needed.

:: When you're sailing, where do you store the shipped oars?

We just leave them banging around, it's kind of untidy but it's OK. We also bring a canoe paddle for tight spots.

For this winter's Covid projects we have :
* investigate oar stowage
* add some kind of "painter" at the stern for tying up at wharves.
* figure out how to use the reef
* fix the styrofoam that busted off the thwarts, maybe build some kind of airtight storage instead? Maybe even replace the middle thwart with a storage box since no-one's ever on it? See above.
* patch up (again) the gouges in the dagger board, rudder, etc.
* investigate a shorter tiller for when I'm sitting at the stern all day
* investigate weird mainsheet tensioner thingy which substitutes for a cleat and makes it easier to hold the sheet. I forget what it's called.