This challenge uses the '+' character

Charcoal, 5 bytes

Ｐ+×+Ｎ

Try it online!

n=2*input()-1;C='+'.center
for c in C(n):print C(n,c)

Try it online!

x=>(v=(` `[r=`repeat`](--x)+`+
`)[r](x))+`+`[r](x*2)+`+
`+v;

2 bytes saved by replacing two occurrences of x-1, the first with --x and the second with x.
2 bytes saved thanks to Kritixi Lithos, replacing "\n" with `[newline]`.
3 bytes saved thanks to user2428118, finally helping me to figure out a way to alias the repeat in a way that reduced the size. (With honourable mention to Marie for her efforts, too)
1 byte saved indirectly thanks to Herman.

f=
x=>(v=(` `[r=`repeat`](--x)+`+
`)[r](x))+`+`[r](x*2)+`+
`+v;
oninput=_=>o.innerText=f(+i.value)
o.innerText=f(i.value=3)

<input id=i min=1 type=number><pre id=o>