You can do these exercises either laying down or standing up, but the key is to be relaxed so if standing up isn't allowing for this, then lay down.
1. Plugging one nostril, breathe in through the unplugged nostril for four counts hold for four counts and then switch nostrils and exhale for four counts. Repeat
2. Plugging one nostril, breathe in through unplugged nostril for four counts, hold for four counts and through a tiny space hissss the air out until you have nothing left, when you are completely out release your jaw with you tongue gently behind your teeth and in as relaxed manner as possible inhale into the depths of your abdomen, a deep breath that fully expands the entirety of your lungs from bottom to top. Repeat.
3. Release your jaw to a open ah position and with your tongue gently resting behind the bottom teeth begin to pant, ensuring that the stomach is loose and allowed to be "fat" not rigid. Do not engage stomach muscles, let the breath move the muscles for you. When pant becomes more eratic less consistent stop, take a breath and start again.  Do this exercise only once as it is very drying.
4. Go back and repeat #3 again and notice both the length of time you are able to release the breath in your sssssss and also the depth of the breath you are able to access when you breathe in again at the end of the exercise.
5. Experiment with the breath and see if you can find the same sensation, depth and level of relaxation when breathing though one nostril and when breathing through the mouth. You can experiment by taking a "nose" breath (only one nostril at a time) and then trying to duplicate the sensation when taking a mouth breath. If there is a lot of tension in the "mouth" breath then try what I call a mixed breath, which is a breath that starts through one nostril for two counts and then the jaw is released and then you breathe through your mouth for two counts.
*** Remember the goal in all of these exercises is to create a sense of profound breath and relaxation***