砦 is a Japanese kanji written with 11 strokes, listed here under the keyword “fort”. It is built from 石 (stone) and 此 (this here). In Remembering the Kanji by James W. Heisig it is frame 2204.
On KumiJi Glyph Explorer, open the parts search and type “stone” + “this here”. 砦 is among the results, together with every other character containing the same shapes.
Open 砦 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.