These steps were used to set up a Raspberry Pi as a wireless access point as a gateway to Tor. The end goal here is the same as OnionPi.

pacman -Syy # Update repos
pacman -Syu # Update system
pacman -Ss hostpad tor bridge-utils dnsmasq
vi /etc/hostapd/hostapd.conf
cat /etc/hostapd/hostapd.conf

ssid=You_Are_Being_Watched
wpa_passphrase=viciousdragon
interface=wlan0
bridge=br0
auth_algs=3
channel=1
driver=nl80211
hw_mode=g
logger_stdout=-1
logger_stdout_level=2
max_num_sta=5
rsn_pairwise=CCMP
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP CCMP

# You can then start the AP using systemd:
systemctl start hostapd.service

vi /etc/tor/torrc
cat /etc/tor/torrc

Log notice file /var/log/tor/notices.log

VirtualAddrNetwork 10.192.0.0/10
AutomapHostsSuffixes .onion.exit
AutomapHostsOnResolve 1

TransPort 9040
TransListenAddress 192.168.192.10

DNSPort 53
DNSListenAddress  192.168.192.11

vi /root/tor_chroot.sh
cat /root/tor_chroot.sh

cat ~/torchroot.sh
#!/bin/bash
export TORCHROOT=/opt/torchroot

mkdir -p $TORCHROOT
mkdir -p $TORCHROOT/etc/tor
mkdir -p $TORCHROOT/dev
mkdir -p $TORCHROOT/usr/bin
mkdir -p $TORCHROOT/usr/lib
mkdir -p $TORCHROOT/usr/share/tor
mkdir -p $TORCHROOT/var/lib

ln -s /usr/lib  $TORCHROOT/lib
cp /etc/hosts           $TORCHROOT/etc/
cp /etc/host.conf       $TORCHROOT/etc/
cp /etc/localtime       $TORCHROOT/etc/
cp /etc/nsswitch.conf   $TORCHROOT/etc/
cp /etc/resolv.conf     $TORCHROOT/etc/
cp /etc/tor/torrc       $TORCHROOT/etc/tor/

cp /usr/bin/tor         $TORCHROOT/usr/bin/
cp /usr/share/tor/geoip* $TORCHROOT/usr/share/tor/
cp /lib/libnss* /lib/libnsl* /lib/ld-linux-*.so* /lib/libresolv* /lib/libgcc_s.so* $TORCHROOT/usr/lib/
cp $(ldd /usr/bin/tor | awk '{print $3}'|grep --color=never "^/") $TORCHROOT/usr/lib/
cp -r /var/lib/tor      $TORCHROOT/var/lib/
chown -R tor:tor $TORCHROOT/var/lib/tor

sh -c "grep --color=never ^tor /etc/passwd > $TORCHROOT/etc/passwd"
sh -c "grep --color=never ^tor /etc/group > $TORCHROOT/etc/group"

mknod -m 644 $TORCHROOT/dev/random c 1 8
mknod -m 644 $TORCHROOT/dev/urandom c 1 9
mknod -m 666 $TORCHROOT/dev/null c 1 3

if [[ "$(uname -m)" == "x86_64" ]]; then
  cp /usr/lib/ld-linux-x86-64.so* $TORCHROOT/usr/lib/.
  ln -sr /usr/lib64 $TORCHROOT/lib64
  ln -s $TORCHROOT/usr/lib ${TORCHROOT}/usr/lib64
fi

At this point, if the AP is running, you should have a br0 bridge:

$ brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.00e01210462b       no              wlan0