This challenge uses the '+' character

Charcoal, 5 bytes

P+×+N

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Python 2, 53 bytes

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

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JavaScript (ES6), 67 65 63 60 59 bytes

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.

Try It

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>