advice need for incinerator

I would like some advice for how to make the best and safest use of my first ever incinerator (Wilko Galvanized Taper Incinerator, 90L). I never had any, but I wanted to start making my own fertiliser, after hearing so often that wood ash is good for fruit trees (apples in part.). I also have a tiny backgarden (see from my logo above), with a ca. 3 x 3m patio in natural sandstone between my house and the green area pictured above. For now, I put the incinerator in a shed. So more precisely my questions are: 1. what's best to burn? 2. how much should I fill it for burning safely? and 3. where is the safest place to put it on: slabs, gravel, or other? Thanks for your advice!

What do you intend to burn?  Wood ash is good.  Do you have a good supply of untreated wood to burn? Do not use any residue from burning plastic on the garden.

 I would certainly try to place the incinerator more than 3m from the house and ensure the smoke is never a nusiance to neighbours enjoying their gardens or hanging out clothes on the line.

I would also ensure the incinerator is not placed directly on sandstone.  It's porous isn't it?

I want to burn the prunings, edge trimming and 2 old big shrubs. Also, weeds, including perennials. I don't use any chemicals, and the wood would come all from natural sources, but possibly damaged, dead or diseased.

Thanks for the advice, I think I will stand it on a metallic big plate for protection below, and on the gravel area (putting away swing seat and all other stuff liable to get damaged by the fire). As for my neighbours, I will make sure that they are not disturbed in any way by the smoke & smell.