於 is a traditional Chinese hanzi, listed here under the keyword “in”. It is built from 方 (a square) and 仒 (kwukyel). It appears as a component in 11 other characters in this index.
On KumiJi Glyph Explorer, open the parts search and type “a square” + “kwukyel”. 於 is among the results, together with every other character containing the same shapes.
Open 於 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.