Eco Matters posted this awesome seed bomb recipe instruction on how these can be made simply (brilliant to make with kids):
Make a seed bomb just as you’d make a mud pie, say the Eco Matters Nature team, then scatter them across slip sites.
1 part seeds,
1 part compost or potting mix to 3 parts clay
Mix all parts together with some water, then roll balls approximately 15-20mm in diameter. Allow to dry for 24 hrs, then ready to use. Keep in a cool area until use.
For an even simpler regeneration technique, if you see a fallen native tree with seed-laden branches, cut those off and scatter them across the bare earth, then let nature do its thing!
If possible, remove the outer fleshy fruit or droop around the seed. This can be done by rubbing the seeds in a sieve to break open the fruit and washing the fleshy pulp away.
How do people gather the seeds? What seeds are best?
It is important to collect all seeds straight from the trees rather than from the ground to prevent the spread of kauri dieback. It is also important to collect from trees in the same area you will be planting (or seed bombing) them in, as these have adapted to local conditions over decades or even millennia.
Always leave some seeds on the tree so it can contribute to the natural process of regeneration. Right now seeds to collect include karamu, kahikatea, kohekohe, manuka and cabbage tree.