this log has proved its self time and time again. it was placed as a geocache and. survived over a two year period only reasion i removed it from play is because the 2nd part was destroyed.
what you need is a completely dry log that is completely covered with bark all the way around
you will need either a hacksaw for a circular saw that will cut the complete depth of the log basically deep enough to cut it in half
some silicone i used black RTV sealant
a router with a hole cutting bit i used a mill and milled out the size hole or pocket i wanted you could use a drill motor with a large bit then chisel out your pocket
some small nails and duct tape safety glasses and gloves
Step 1: Making the Cut
cut your log with the bark on and be careful not to damage it or break any of it off if you do keep it all is not lost. if you made a clean cut you now have to hide a logs.
Step 2: Separate the Bark
remove bark and try to keep it in one piece. once removed coat the underside with the RTV use alot set that aside to dry make sure its smooth and completely covered this point you can try and stick any pieces that broke off if any
Step 3: Cut Out Your Pocket
whatever method you choose to use cut up the desired whole or pocket in your log using your duct tape make a flap that will cover your pocket or whole completely I silicone the edges to make it watertight and use the nails to secure it like a hinge
Step 4: Fit the Top and Trim Cover If Needed
you may need to trim recover a little bit to make it fit snugly without any gaps I added a wireless doorbell I found it Harbor Freight just to make it a little more advanced you don't have to if you don't want to it originally was in place for over 2 years without it