The Unilateral Bodyweight Calf Raise
You can do this first variation in your gym on a step or at home. And if your calves are lagging, you can do it every day.
First, pick a total amount of reps to aim for using bodyweight only, like 100. Start by doing as many reps as possible on one leg, then immediately switch to the other leg. Continue in this manner without rest until your total rep goal is reached.
So let's say you do 25 reps to start with on the left leg. You then switch to the right leg and do 25 reps. Then immediately go back to the left leg and continue. Repeat this process until you meet your TOTAL rep goal.
The Staircase Option
There's another fun way to do these if you have access to stairs. Do a set number of reps with each leg on each step. For example, you have 12 steps on the set of stairs. That's 12 sets in front of you. For each step do a certain amount of reps for each leg. This will vary of course depending on how much you like pain.
For staircases that have a lot of steps, I'd suggest 5 reps. For 10 steps or fewer, go with 8-10 reps. Just have some fun with it.