An easy safety box to make, is a cheap metal tool box. Mine is lined with plaster board covered with glass cloth. There is a vent hole in the top of the box with glass cloth to retard flames (glass cloth will withstand a gas flame without burning so should slow down a LiPo flame for a period of time ) The box is not locked when in use and the lid is left sitting to avoid gas build-up in the event of a fire.
A good idea with LiPos is to monitor them constantly and ALWAYS balance charge. If you see 1 cell going over the 4.2V max (can happen even with good chargers) and the others are around 4.16/.18/.19, stop the charger and put the batteries on a separate balancer until they even out, then it should be good to use, even though the voltage is a bit less. As long as your battery is not too puffed, (a small amount of softness after a large draw is ok - you can put it in the fridge/ chilly bin for a few minutes if they are warm, and it will usually return to normal.
If they puff a big amount and stay that way, get rid of them. Discharge them in a bucket of really salty water for a week until they stop bubbling at the terminals. I usually cut the balance and main leads off before I do (outside, one wire at a time, making really sure you don't short anything) to use later. Once the battery is discharged, take it out to the middle of the lawn and put a large nail or garden fork right through it and leave it for a while, to make sure it's well and truly dead before disposing of it .
I have LiPos I'm still using from 2011. If you treat them well they can last for years (buy good quality batteries like Hyperion or similar, cheap ones can be dangerous.) You might pay a bit more but they should last a long time.
Balance charge them, don't over draw them , don't drop them, don't have sharp objects (modelling knives etc) round them on the bench, discharge them to storage after use, don't leave them in the hot sun, and NEVER short them, and they will be good for years. Nothing special,- just common sense.
If you are scared of LiPos, try (DON'T) shorting a fully charged car battery and see what happens, be sure to wear an acid proof full suit, respirator and have a decontamination shower handy 😮💥 All batteries are dangerous even NiMH and NiCad's which can cause fires if shorted or go bang.