Route VPN Through Android Hotspot With Root

make your phone to act as a VPN Gateway
Requirements:

root

vpn server (can obtain any free openVPN from playstore)

Using a VPN gateway will make tethered traffic to go through the VPN.
Steps

Turn on portable hotspot

Open terminal as root and enter the following codes (you can paste them)
iptables -t filter -F FORWARD iptables -t nat -F POSTROUTING iptables -t filter -I FORWARD -j ACCEPT iptables -t nat -I POSTROUTING -j MASQUERADE ip rule add from 192.168.43.0/24 lookup 61 ip route add default dev tun0 scope link table 61 ip route add 192.168.43.0/24 dev wlan0 scope link table 61 ip route add broadcast 255.255.255.255 dev wlan0 scope link table 61

Edit
If you are not rooted you can use PdaNet+.