You can do that by dissolving aluminum in hydrochloric acid and boiling off the HCL. The reaction produces hydrogen, hot HCl fumes and may spit as the liquid is boiled to dryness. Pretty dangerous stuff! It is much easier and safer to buy the aluminum chloride as aluminum chlorohydrate.
Aluminum chloride (AlCl3, anhydrous) will react with water aggressively to form aluminum chlorohydrate and hydrochloric acid. Since you intend to make up an aqueous solution of this, you could start with aluminum chlorohydrate.